Tire

ABSTRACT

In a pneumatic tire 10 according to the present invention, as an average sipe interval hc defined by an average interval of sipes adjacent to each other in a tire circumferential direction in a center portion block, which is a block arranged at a position including a tire equatorial line, and an average sipe interval hs is defined in a shoulder portion block, which is a block located at an ground contact end in a tire width direction, a relation of 1.05≤(hs/hc)≤4.00 is fulfilled.

TECHNICAL FIELD

The present invention relates to a tire such as a studless tire, capableof travelling on ice and snow roads.

BACKGROUND ART

Conventionally, in a studless tire having both of performance on ice andsnow roads and performance on dry roads, it is extremely important thatthe performance on the ice and snow roads and the performance on the dryroads are derived to be balanced well.

The studless tire is required to enhance the performance on the dryroads in addition to high performance on the ice and snow roads.

Thus, in order to derive both of driving force on the ice and snow roads(snow traction) and driving force on the dry roads (dry roads) (drytraction) at a high level, a configuration to determine a relationbetween a density of a sipe formed in a tread and a pitch length definedby a repeating unit of a shape of the tread is disclosed (for example,see Patent Literature 1).

CITATION LIST Patent Literature

-   [PTL 1] Japanese Translation of PCT International Application    Publication No. 2014-531365

SUMMARY OF INVENTION

In not only a studless tire but also a tire including a land portionblock defined by a circumferential direction groove extended in a tirecircumferential direction and a lug groove extended in a tire widthdirection, it is known that, by increasing the number of the sipesformed in the land portion block, an edge component that scratches theroad surface can be increased, and therefore braking performance on theice and snow road, in particular an ice road surface is improved.

On the other hand, when the number of the sipes formed in the landportion block is increased, the rigidity of the land portion block(block rigidity) is deteriorated, and thereby improvement of otherperformance is interrupted. When the block rigidity is deteriorated, inaddition to the deterioration of the braking performance on the ice roadsurface as described above, especially wear resistant performance on adry road surface is largely deteriorated.

Specifically, when the number of the sipes formed in the land portionblock is increased, the block rigidity of a whole of the land portionblock is largely deteriorated. Thus, an end portion of the land portionblock at a kick-out side is easily lifted off the road surface inaccelerating or braking. As a result, wear of the land portion blockproceeds so that the tire lifetime is shortened.

Further, in a winter tire such as a studless tire, it is necessary tostop a car on the ice road surface, namely on-ice performance in a tirecircumferential direction required in braking on the ice road surface isimportant. By forming the sipe in the land portion block, the on-iceperformance is improved. Thus, the on-ice performance has been improvedby forming as many sipes as possible in one land portion block.

For example, the number of the sipes is increased by arranging the sipesadjacent to each other to face in the tire circumferential direction soas to be parallel to a tire width direction, which is a direction inwhich an edge effect appears to be close to each other as much aspossible, or alternatively, by arranging a side wall at an end in acircumferential direction of the land portion block that receives inputin the tire circumferential direction in braking and the sipe to beparallel to each other and to be close to each other as much aspossible.

Conventionally, by setting a sipe interval as small as possible and byforming the sipe tightly in the land portion block as described above,the edge effect by an sipe edge has been improved.

Further, a pitch length defined by a length in the tire circumferentialdirection of a pitch of the land portion block as one basic unit of atread pattern continuously repeated in the tire circumferentialdirection, or a length in the circumferential direction of the landportion block is made long so that the rigidity of the land portionblock (block rigidity) is increased and the falling of the land portionblock is suppressed. Consequently, a ground contact area of the landportion block is increased, and thereby the on-ice performance and thewear resistant performance have been improved.

However, the sipe density in the land portion block has been alreadyincreased to its limit, and therefore the sipe interval cannot be madesmall any more. Further, even if the pitch length is made long and thelength in the circumferential direction of the land portion is madelong, when the land portion block is finely divided by the sipes, theblock rigid is deteriorated.

Further, when the pitch length or the length in the circumferentialdirection of the land portion is made long, the number of the pitches orthe land portion blocks within the ground contact length is decreased.Thus, when the number of the pitches or the land portion blocks isfurther decreased, the length in the circumferential direction of theland portion becomes long excessively. Consequently, an area of a luggroove is decreased so that draining performance is deteriorated, and ablock edge component by the lug groove is not derived. The conventionaltire described above cannot solve such problems.

In this way, a certain relation exists between a property of the landportion block and a property of the sipe formed in the land portionblock, however there is a room for a further study relating to therelation of the both properties capable of deriving the performance onthe ice road surface and the performance on the dry road surface at ahigh level.

Accordingly, an object of the present invention is, in consideration ofthe problem described above, to provide a tire such as a studless tirecapable of travelling on ice and snow roads including an ice roadsurface and capable of deriving performance on the ice road surface,performance on a dry road surface, and especially wear resistantperformance at a high level.

The present inventors conducted a study of a relation between a vehicleproperty and a ground contact state of a tire surface relating toimprovement of the on-ice performance in braking. As a result, aknowledge that, in a vehicle having an anti-lock brake system (ABS) asgenerally installed in most vehicles in recent years, a ground contactsurface of a tread of the tire contacted with the ice road surface isrenewed constantly without locking a wheel in braking and thereby awater screen is hardly interposed between the ice road surface and thetire surface in travelling on the ice road surface, compared to aconventional ABS non-installed vehicle, was obtained.

Based on this knowledge, in the ABS installed vehicle, it was found thatthe on-ice performance is obtained effectively by securing the groundcontact area largely rather than improving the edge effect. Thus, thepresent inventors conducted a study relating to improvement of theon-ice performance in braking, based on a viewpoint of a configurationof a tire (tread pattern), and as a result, the following techniqueswere derived.

At first, by setting the sipe interval to be large, the block rigiditycan be increased. With this, falling of the land portion block issuppressed, and thereby a ground contact area is increased, forcepressing a block edge and the sipe edge against a road surface isincreased, and the edge effect is improved. Further, as a result, thewear resistant performance is improved.

Here, in the present invention, the block rigidity denotes the blockrigidity in the tire circumferential direction required in braking onthe ice road surface unless otherwise mentioned.

Here, when the sipe interval is made large, the number of the sipesformed in the land portion block becomes small, and therefore the edgeeffect by the sipe edge is deteriorated. Thus, by further setting thepitch length of the land portion block to be small, the number of blocksin a whole circumference of the tire is increased. Consequently, theedge effect by the block edge, which is larger in the edge effect thanthe edge effect by the sipe edge, is improved instead of thedeteriorated edge effect by the sipe edge, so that the total edge effectis improved.

That is, by setting the sipe interval to be large and by setting thepitch length of the land portion block to be small, the block rigidityis increased, and thereby the falling of the land portion block issuppressed and the ground contact area is increased. Further, when theforce pressing the block edge and the sipe edge against the road surfaceis increased and the block edge is improved, the wear resistantperformance is improved while improving the total edge effect.

As a result, the braking performance on the ice road surface, theperformance on the dry road surface, and especially the wear resistantperformance can be obtained at a high level.

Accordingly, in one aspect of the present invention, a tire includes acircumferential direction groove extended in a tire circumferentialdirection, a lug groove extended in a tire width direction, and aplurality of blocks defined by the circumferential direction groove andthe lug groove. At least one of the blocks includes one or more sipesextended in the tire width direction. As an average sipe interval hc isdefined by an average interval of the sipes adjacent to each other inthe tire circumferential direction in a center portion block, which isthe block arranged at a position including a tire equatorial line, andan average sipe interval hs is defined by an average interval of thesipes adjacent to each other in the tire circumferential direction in ashoulder land portion block, which is the block located at a groundcontact end in the tire width direction, a relation of 1.05≤(hs/hc)≤4.00is fulfilled.

In one aspect of the present invention, as an average sipe interval h₂is defined by an average interval of the sipes adjacent to each other inthe tire circumferential direction in a second land portion block, whichis the block located at an outer side in the tire width direction of thecenter portion block, a relation of 1.00≤(h₂/hc)≤7.00 may be fulfilled.

In one aspect of the present invention, s an average sipe interval h₂ isdefined by an average interval of the sipes adjacent to each other inthe tire circumferential direction in a second land portion block, whichis the block located at an outer side in the tire width direction of thecenter portion block, and the average sipe interval hs is defined by theaverage interval of the sipes adjacent to each other in the tirecircumferential direction in the shoulder land portion block, which isthe block located at the ground contact end in the tire width direction,a relation of 0.97≤(hs/h₂)≤2.15 may be fulfilled.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view of a whole of a pneumatic tire10.

FIG. 2 is an enlarged perspective view of a part of the pneumatic tire10.

FIG. 3 is a plane developed view of a part of a tread 20.

FIG. 4 is an enlarged plane view of a part of a V-shape land portion row100.

FIG. 5 is an enlarged plane view of a part of a V-shape land portionblock 101 forming the V-shape land portion row 100.

FIG. 6 is an enlarged plane view of a part of a center land portion row200.

FIG. 7A is a view for describing rotation moment generated in a landportion block 210.

FIG. 7B is a view for describing rotation moment generated in a landportion block 210P in a conventional configuration.

FIG. 8 is an enlarged plane view of a part of a shoulder land portionrow 300 in.

FIG. 9 is an enlarged perspective view of a land portion block 310forming the shoulder land portion row 300 in.

FIG. 10 is a view illustrating definitions of respective lengths in theV-shape land portion row 100.

FIG. 11 is a view illustrating definitions of respective lengths in thecenter land portion row 200.

FIG. 12 is a view illustrating definitions of respective lengths in theshoulder land portion row 300 in.

FIG. 13 is a plane developed view of a part of a pneumatic tire 10Ahaving a pitch different from that of the pneumatic tire 10 shown inFIG. 1 through FIG. 12.

DESCRIPTION OF EMBODIMENTS

Next, embodiments will be described with reference to the drawings.Further, the same or similar reference numerals are used to designatethe same or similar parts, and the description thereof is omitted asneeded.

(1) Schematic Configuration of Whole of Tire

FIG. 1 is a schematic perspective view of a whole of a pneumatic tire 10according to the present embodiment. FIG. 2 is an enlarged perspectiveview of a part of the pneumatic tire 10. Here, in FIG. 1 and FIG. 2, anillustration of a part of a pattern (tread pattern) formed in a tread 20is omitted. FIG. 3 is a plane developed view of a part of the tread 20.

As shown in FIG. 1 through FIG. 3, the pneumatic tire 10 is formed as atire so-called studless tire adapted to travel on ice and snow roads, inparticular an ice road surface. In the pneumatic tire 10, a rotationdirection is not designated, however shoulder land portion rows to belocated at an inner side (vehicle hub side) and at an outside whenmounted to a vehicle are defined (see FIG. 2).

A plurality of land portion rows contacted with a road surface is formedin the tread 20 of the pneumatic tire 10. Specifically, a V-shape landportion row 100, a center land portion row 200, and shoulder landportion rows 300 in, 300 out are formed in the tread 20.

The V-shape land portion row 100 is offset from a position of a tireequatorial line CL (not shown in FIG. 1 and FIG. 2, see FIG. 3).Specifically, the V-shape land portion row 100 is arranged at a side ofa tread end with respect to the tire equatorial line CL.

The center land portion row 200 is arranged adjacent to the V-shape landportion row 100 and arranged at a position including the tire equatorialline CL.

The shoulder land portion row 300 out is arranged adjacent to the centerland portion row 200 and arranged at an outer side with respect to thecenter land portion row 200 when mounted to a vehicle.

The shoulder land portion row 300 in is arranged adjacent to the V-shapeland portion 100 and arranged at an inner side with respect to theV-shape land portion 100 when mounted to the vehicle.

A plurality of circumferential direction grooves extended in the tirecircumferential direction is formed in the tread 20. Specifically, acircumferential direction groove 30 is formed between the V-shape landportion row 100 and the center land portion row 200.

A circumferential direction groove 40 is formed between the V-shape landportion row 100 and the shoulder land portion row 300 in. Acircumferential direction groove 50 is formed between the center landportion row 200 and the shoulder land portion row 300 out.

Further, a circumferential direction groove 60 is formed between a landportion row 201 and a land portion row 202 that form the center landportion row 200.

Further, a lug groove 70 extended in the tire width direction is formedin the shoulder land portion row 300 out, and a lug groove 80 extendedin the tire width direction is formed in the shoulder land portion row300 in.

Further, an element of the land portion that forms the land portion rowand contacts with the road surface is described as a land portion block(alternatively, merely block).

It is preferable that rubber (tread rubber) forming such tread 20 isformed of foamed rubber. The reason that the foamed rubber is preferableis the compression deformation is easily generated due to an effect inwhich a rubber solid phase part is replaced with an air phase partbecause an air hole is included in the foamed rubber.

With this, increase of the ground contact area by the flexibility,removal of the water screen that largely decreases a frictioncoefficient μ on the ice road surface by the holes of foaming on thetread surface, and improvement of the edge effect, which is similar tothat caused by the sipe edge component or the block edge component, bythe micro edge due to the scratching of the holes of the block foamingare remarkable.

The tread rubber has a structure having two layers or more of a surfacerubber and an inner rubber. It is preferable that the foamed rubber isused in the surface rubber, and the inner rubber is formed of non-foamedrubber or formed rubber having elastic modulus larger than that of thesurface rubber. Further, it is preferable that the surface rubber isused in a portion having a depth to a snow platform in a radialdirection that indicates a usage limit due to wear, and the inner rubberis used in a portion inner than the snow platform in the radialdirection.

The foamed rubber includes air holes therein and has low elasticmodulus, the rigidity of a whole of the land portion block (land portionblock) is secured by the rigidity of the inner rubber. The foaming ratiois preferably set in a range between 3% and 40%. When the foaming ratiois 40%, the elastic modulus of the foamed rubber is 60% of the elasticmodulus of the non-foamed rubber. Thus, in a case in which the foamingratio is more than 40%, the elastic modulus of the foamed rubber isexcessively low, and therefore the rigidity of the whole of the landportion block cannot be secured by any shape of the land portion block.

When the foaming ratio is 3%, the elastic modulus of the foamed rubberis 97% of the elastic modulus of the non-foamed rubber, and thereforethe block rigidity can be secured. However, in a case in which thefoaming ratio is less than 3%, the flexibility due to the air holes ofthe foaming, the removal of the water screen, and the edge effect cannotbe obtained. More preferably, the foaming ratio is set in a rangebetween 12% and 32%. In this range, securing of the block rigidity, theground contact area by the flexibility, the removal of the water screen,and the edge effect can be obtained at a high level.

Further, in a winter tire such as a studless tire, the elastic modulusof the tread rubber contacted with the road surface is made low in orderfor the increase of the friction coefficient μ against the ice roadsurface and the increase of the ground contact area by the flexibility.However in the non-foamed rubber, in the composition of the non-foamedrubber for the tread rubber, by decreasing an addition amount of carbon,by adopting polymer having low elastic modulus within a usagetemperature range, or by lessening a vulcanizing addition amount tosuppress cross-linking, the wear performance is deteriorated.

Further, when the tread rubber is made low in the elastic modulus byincreasing the oil addition amount, in the produced tire aftervulcanizing, the oil is transferred to an outside of the tread rubber,and thereby the elastic modulus becomes high due to aging of a half yearthrough one year. Consequently, the tread rubber is hardened and therebythe flexibility disappears. On the other hand, in the foamed rubber, theflexibility is secured by the air holes therein, and thereby contrary tothe oil, foaming holes therein does not disappear due to the aging.

Further, in the composition of the rubber solid phase part other thanthe rubber, the carbon addition amount can be made large, the elasticmodulus of the polymer within the usage temperature range can be madehigh, and the vulcanizing addition amount can be made large. With this,extremely high elastic modulus of the foamed rubber having excellentwear performance can be obtained without increasing the oil additionamount. Even if the foamed rubber is made high in the elastic modulus,by setting the foaming ratio to 20%, the foamed rubber can be formed aslow elastic modulus rubber with 80% of the elastic modulus of thenon-foamed rubber, due to the replacement of the air holes.

In the pneumatic tire 10, by using the flexibility and easiness of thecompression deformation of the foamed rubber in which the elasticmodulus can be made lower against the elastic modulus of the normalnon-foamed rubber as the amount of foaming is increased, a shape of theland portion block can be made extremely high in the rigidity.

The elastic modulus of the rubber is set in a range between 2.0 MPa and5.0 MPa, preferably in a range between 2.3 MPa and 3.5 MPa. The rubberis preferably formed of foamed rubber. The foaming ratio is set in arange between 3% and 40%, preferably in a range between 12% and 32%.

The elastic modulus of the rubber (unit MPa) is a measurement value at atemperature of 23° C. according to Japanese Industrial Standards. Theelastic modulus is measured by using a spectrometer produced by UeshimaSeisakusho Co., Ltd. under a condition of initial strain of 2%, dynamicstrain of 1%, and frequency of 52 Hz. A dynamic tensile storage elasticmodulus E′ at a temperature of 23° C. is defined as the elastic modulus.

Large value of the elastic modulus denotes high elasticity.

Here, the measured elastic modulus is the dynamic tensile storageelastic modulus E′ in a dynamic tensile viscoelasticity test. However,in other tests such as a dynamic compression viscoelasticity test, adynamic shear viscoelasticity test and other dynamic viscoelasticitytest, the result thereof is similar to the result in the dynamic tensileviscoelasticity test, and therefore as the foaming ratio is larger,lower elasticity is shown.

Accordingly, a configuration of the elastic modulus of the tiredescribed in the present embodiment is satisfied in the dynamicviscoelasticity test under the measurement condition described above ormeasurement conditions equivalent thereto. The reason is that thetensile elastic modulus, the compression elastic modulus, and the shearelastic modulus of rubber used in the tread portion of the tire areproportional to each other because the Poisson's ratio of rubber isclose to 0.5 and a change in volume of the rubber is extremely smallwhen the rubber is deformed.

(2) Configuration of Tread 20

Next, a configuration of the tread 20 will be described. Specifically,each of shapes of the V-shape land portion row 100, the center landportion row 200 and the shoulder land portion row 300 out will bedescribed.

(2.1) V-Shape Land Portion Row 100

FIG. 4 is an enlarged view of a part of the V-shape land portion row100. The V-shape land portion row 100 is provided with the land portionblock defined by the circumferential direction groove 30, thecircumferential direction groove 40, and a width direction inclinedgroove 160 (lug groove). Specifically, the V-shape land portion row 100is provided with a plurality of V-shape land portion blocks 101 alongthe tire circumferential direction.

The V-shape land portion block 101 is provided with a projection portionprojected toward one side in the tire circumferential direction, and arecess portion recessed toward the one side in the tire circumferentialdirection, so that the V-shape land portion block 101 is formed in aV-shape in the tread surface view. Specifically, the V-shape landportion block 101 is formed as a V-shape land portion block having aprojection portion 110 and a recess portion 120. Further, the V-shapeland portion block 101 denotes a block formed in a V-shape or achevron-like shape in the tread surface view.

In the tread surface view, an inclined angle θ1 (inclined direction) ofa projection portion side wall 111 of the V-shape land portion block 101that forms the projection portion 110, against the tire width directionis the same (same direction) as an inclined angle θ2 of a recess portionside wall 121 that forms the recess portion 120, against the tire widthdirection. Similarly, an inclined angle θ3 (inclined direction) of aprojection portion side wall 112 of the V-shape land portion block 101,against the tire width direction is the same (same direction) as aninclined angle θ4 of a recess portion side wall 122 that forms therecess portion 120, against the tire width direction. Here, the inclinedangles are not necessarily the same to each other, and “the same” or“the same direction” denotes a case in which the difference between theinclined angles is 20 degree or less (hereinafter, this is similarlyapplied to the description of the inclined angle).

The inclined angles of the projection portion side wall 111, the sipe130, and a terminal inclined groove 150 at a side of the tire equatorialline CL, and the inclined angles of the projection portion side wall112, and the sipe 140 at a side of the tread end are preferably set suchthat the inclined angles at one side is in a range between 15° and 35°,and the inclined angles at another side is in a range between 7° and 25°against the tire width direction. In the present embodiment, the anglesof θ1, θ2, θ5, and θ6 (one side) shown in FIG. 4 are the same to eachother, and the angles of θ3, θ4, θ7, θ8, and θ9 (another side) are thesame to each other.

By setting the inclined angles of the two side walls located at the sideof the projection portion 110 of the V-shape land portion block 101,against the tire width direction to be in such ranges, the edge effectby the block edge and the sipe edge in the tire circumferentialdirection can be especially enhanced.

A plurality of the sipes inclined against the tire width direction isformed in the V-shape land portion block 101. Specifically, the sipe 130and the sipe 140 are formed. Each of the sipe 130 and the sipe 140 isinclined against the tire width direction, while the sipe 130 isinclined opposite to the sipe 140 against the tire width direction.

In the present embodiment, each of the sipe 130 and the sipe 140 isformed in a zigzag shape. Specifically, each of the sipe 130 and thesipe 140 is bent against its extending direction (at once or severaltimes) in the tread surface view and formed in a linear shape in thetire radial direction. Or alternatively, each of the sipe 130 and thesipe 140 may be bent in both of its extending direction and the tireradial direction. Or alternatively, each of the sipe 130 and the sipe140 may be bent in the tire radial direction and formed in a linearshape in its extending direction. Or alternatively, each of the sipe 130and the sipe 140 may be formed in a linear shape in the tire radialdirection and formed in a linear shape in its extending direction. Here,the sipe is a fine groove closed in the ground contact surface of theland portion block. An opening width of the sipe in a ground non-contactstate is not especially limited, however the opening width is preferablyset in a range between 0.1 mm and 1.5 mm.

Further, a terminal inclined groove inclined against the tire widthdirection is formed in the V-shape land portion block 101. Specifically,the terminal inclined groove 150 is formed in the V-shape land portionblock 101 at a side of the tire equatorial line CL.

Here, to be inclined against the tire width direction denotes that notto be parallel to the tire width direction so as to form a predeterminedangle against the tire width direction, and therefore to be inclinedagainst the tire width direction excludes a state to be parallel to thetire circumferential direction (namely, an angle against the tire widthdirection is 90 degrees).

An inclined angle θ5 (inclined direction) of the terminal inclinedgroove 150 against the tire width direction is the same as the inclinedangle θ1 (inclined angle θ2) of the projection portion side wall 111against the tire width direction, namely the inclined angles are thesame direction. Similarly, an inclined angle of the sipe 130 against thetire width direction is the same (same direction) as the inclined angleθ1 (inclined angle θ2) of the projection portion side wall 111 againstthe tire width direction. Further, a relation between the recess portionside wall 121 and the sipe 130, a relation between the projectionportion side wall 112 and the sipe 140, and a relation between therecess portion side wall 122 and the sipe 140 are similar to therelation described above.

One end of the sipe 130 is opened to a side wall 100 a of the V-shapeland portion block 101 in the tire width direction. On the other hand,another end of the sipe 130 is terminated in the V-shape land portionblock 101. Specifically, an end 131 of the sipe 130 is terminated in theV-shape land portion block 101.

Similarly, one end of the terminal inclined groove 150 is opened to theside wall 100 a at a side of the tire equatorial line CL. On the otherhand, an end 151 of the terminal inclined groove 150 is terminated inthe V-shape land portion block 101.

A circumferential direction length along the tire circumferentialdirection of the V-shape land portion block 101 is longer than a widthdirection length along the tire width direction of the V-shape landportion block 101. Here, the circumferential direction length of theV-shape land portion block 101 denotes a length of the longest portionof the V-shape land portion block 101 in the tire circumferentialdirection, specifically “a circumferential direction length” shown inFIG. 10 described below. The width direction length of the V-shape landportion block 101 denotes a length between the side wall 100 a and aside wall 100 b, specifically “a width direction length” shown in FIG.10.

A communication sipe communicated with the terminal inclined groove 150is included in the sipes 140 formed in the V-shape land portion block100. Specifically, a communication sipe 141 is included in the sipe 140.

One end of the communication sipe 141, specifically an end 141 a, iscommunicated with an end 151 served as a terminal portion of theterminal inclined groove 150. Another end of the communication sipe 141is opened to the side wall 100 b of the V-shape land portion block 101in the tire width direction. The side wall 100 b is a side wall of theV-shape land portion block 101 at a side of the tread end in the tirewidth direction.

In the tread surface view, a side wall 100 c of the V-shape land portionblock 101 that forms the terminal portion (end 151) of the terminalinclined groove 150 is continued to the communication sipe 141 on anextension line of the communication sipe 141. A position of the terminalportion of the terminal inclined groove 150 is different from a positionof the most projected portion 110 a of the projection portion 110, inthe tire width direction.

Further, the terminal inclined groove 150 is extended in the samedirection as the sipe 130 formed at a side of an opening end of theterminal inclined groove 150 with respect to most recessed portion 120 aof the recess portion 120. The sipe 130 is formed at the side of theopening end of the terminal inclined groove 150 with respect to the mostrecessed portion 120 a. The sipe 140 is formed at a side of a terminal(end 151) of the terminal inclined groove 150 with respect to the mostrecessed portion 120 a.

The most projected portion of the projection portion 110 and the mostrecessed portion of the recess portion 120 denote the maximum projectedpoint and the maximum recessed point as bent points of the projectionportion 110 and the recess portion 120, respectively. In a case in whicheach of the projection portion 110 and the recess portion 120 is formedin a trapezoidal shape having two bent points, each of the projectionportion 110 and the recess portion 120 has a plurality of the bentpoints, or each of the projection portion 110 and the recess portion 120is formed in a curved trapezoidal shape having a certain range of themaximum projected point or the maximum recessed point in the tire widthdirection, the most projected portion of the projection portion 110 andthe most recessed portion of the recess portion 120 denote the centerpositions in the range in the tire width direction.

In the present embodiment, the most projected portion 110 a is locatedat a side of the tread end with respect to the most recessed portion 120a.

A length of the terminal inclined groove 150 is the same as a length ofthe sipe 130 formed at the side of the opening end of the terminalinclined groove 150. The length of the terminal inclined groove 150denotes a length of the terminal inclined groove 150 along the extendingdirection of the terminal inclined groove 150. The length of the sipe130 denotes a length of the sipe 130 along the extending direction ofthe sipe 130.

The terminal inclined groove 150 is inclined and extended in the samedirection as the sipe 130 formed at a side of the tire equatorial lineCL with respect to the center of the V-shape land portion block 101 inthe tire width direction.

The V-shape land portion block 101 includes a V-shape land portion block101A (first block) and a V-shape land portion block 101B (second block)adjacent to each other in the tire circumferential direction. In thisway, the V-shape land portion blocks 101 are arranged at a plurality ofpositions along the tire circumferential direction.

A width direction inclined groove inclined against the tire widthdirection is formed between the V-shape land portion block 101A and theV-shape land portion block 101B. Specifically, a width directioninclined groove 160 having one bent portion is formed between theV-shape land portion block 101A and the V-shape land portion block 101B.

Specifically, the width direction inclined groove 160 is provided withan inclined groove portion 161 (first inclined groove portion) locatedat one side in the tire width direction with respect to a bent portion163, and an inclined groove portion 162 (second inclined groove portion)located at another side in the tire width direction with respect to thebent portion 163. The inclined groove portion 161 is located at a sideof the opening end of the terminal inclined groove 150, namely at a sideof the tire equatorial line CL with respect to the bent portion 163. Theinclined groove portion 162 is located at a side of the terminal (end151) of the terminal inclined groove 150 with respect to the bentportion 163.

The bent portion 163 is bent at each of a position of the projectionportion 110 of the V-shape land portion block 101A and a position of therecess portion 120 of the V-shape land portion block 101B. That is, thebent portion 163 is bent at the positions of the projection portion 110and the recess portion 120 offset to each other in the tire widthdirection. Consequently, a circumferential length (groove length) alongthe tire circumferential direction of the width direction inclinedgroove 160 is uneven in the tire width direction. Specifically, thecircumferential direction length of the inclined groove portion 161 andthe circumferential direction length of the inclined groove portion 162are different from each other, and the circumferential direction lengthof the inclined groove portion 161 is longer than the circumferentialdirection length of the inclined groove portion 162.

Further, a linear line between the most projected portion 110 a and themost recessed portion 120 a is a boundary between the inclined grooveportion 161 and the inclined groove portion 162. A total length of aline between a center point in the tire circumferential direction on theboundary and a center point in the tire circumferential direction of theend of the inclined groove portion 161 opposite to the boundary and aline between the boundary and a center point in the tire circumferentialdirection of the end of the inclined groove portion 162 opposite to theboundary is called width direction length.

The terminal inclined groove 150 is inclined and extended in the samedirection as the inclined groove portion 161. The sipe 130 is alsoextended in the same direction as the inclined groove portion 161. Thesipe 140 is extended in the same direction as the inclined grooveportion 162.

The V-shape land portion block 101 is arranged in a center regionincluding the tire equatorial line CL or in a second region located atan outer side in the tire width direction of the center region.

In the present embodiment, in the land portion blocks defined by thecircumferential grooves and the lug grooves, a land portion blocklocated at a ground contact end is called a shoulder portion landportion block, a land portion block located at an inner side in the tirewidth direction adjacent to the shoulder portion land portion block iscalled a second portion land portion block, and a land portion blocklocated at the inner side in the tire width direction adjacent to thesecond portion land portion block and including the tire equatorial lineCL is called a center portion land portion block.

Further, regions included in the center portion land portion block, thesecond portion land portion block, and the shoulder portion land portionblock are called a center region, a second region, and a shoulderregion, respectively.

In a case in which the center portion land portion block is formed inone row within the tire width direction, the center region is a regionof 16% (W/2×0.16) from the tire equatorial line CL, namely a groundcontact center, which is a half of a ground contact width (W) of thepneumatic tire 10, in the tire width direction, and the shoulder regionis a region of 42% (W/2×0.42) from a ground contact end, and the secondregion is a region of 42% (W/2×0.42) of the ground contact width (W) andis located at an inner side in the tire width direction with respect tothe shoulder region.

In a case in which the center portion land portion block rows are formedin two rows adjacent to each other in the tire width direction, thecenter region is a region of 22% (W/2×0.2) from the tire equatorial lineCL, namely the ground contact center, which is a half of the groundcontact width (W) of the pneumatic tire 10, in the tire width direction,and the shoulder region is a region of 39% (W/2×0.39) from the groundcontact end, and the second region is a region of 39% (W/2×0.39) of theground contact width (W) and is located at the inner side in the tirewidth direction with respect to the shoulder region.

In a case in which the land portion block is formed across a pluralityof regions of the center region, the second region and the shoulderregion, the region that occupies the maximum area is defined as the landportion block. For example, in a case in which the center regionoccupies an area of the land portion block larger than an area of theland portion block occupied by the second region, the land portion blockis defined as the center land portion block.

Further, in a case in which determination of the definition position ofthe center portion land portion block, the second portion land portionblock and the shoulder portion land portion block by the circumferentialdirection grooves is difficult due to a shape of the circumferentialdirection groove (land portion block) or the like, the land portionblock in the center region is defined by a range of the center portionland portion block, the land portion block in the second region isdefined by a range of the second portion land portion block, and theland portion block in the shoulder region is defined by a range of theshoulder portion land portion block.

Further, the ground contact width (W) denotes a length in the tire widthdirection of the tread 20 contacted with a road surface when a normalload is applied to the pneumatic tire 10 filled with air of normalinternal pressure. Similarly, the ground contact surface (ground contactarea) denotes a part of the tread 20 contacted with the road surfacewhen a normal load is applied to the pneumatic tire 10 filled with airof the normal internal pressure.

The normal internal pressure denotes air pressure corresponding to themaximum load capacity defined in Year Book of JATMA (Japan AutomobileTyre Manufacturers Association). The normal load denotes the maximumload capacity (maximum load) corresponding to the maximum load capacitydefined in JATMA Year Book.

A negative ratio of the V-shape land portion block 101 is set in a rangebetween 2.5% and 30%. The negative ratio is preferably set in a rangebetween 2.5% and 12.5%.

The negative ratio of the V-shape land portion block 101 denotes, whenan area of the V-shape land portion is defined by an area including theterminal inclined groove 150 and a notched recess portion 170 in theV-shape land portion 101 (hereinafter the same), a ratio of the totalarea of the terminal inclined groove 150 and the notched recess portion170 to the area of the V-shape land portion block 101. That is, thenegative ratio of a whole of the pneumatic tire 10, and a groove arearatio which is a ratio of the total area of the groove to the groundcontact area of the tire including the area of the groove are calculatedat one land portion block. Further, the sipe is closed in the groundcontact surface, and therefore the area thereof is zero.

Further, a negative ratio of the V-shape land portion row 100 is set ina range between 6% and 36%. The negative ratio is preferably set in arange between 8% and 23%.

The negative ratio of the V-shape land portion row 100 denotes, when anarea of the V-shape land portion row 100 between the side walls (sidewall 100 a and side wall 100 b) at both sides in the tire widthdirection is defined by an area including the terminal inclined groove150, the notched recess portion 170 and the width direction inclinedgroove 160 in the V-shape land portion row 100, a ratio of the totalarea of the terminal inclined groove 150, the notched recess portion 170and the width direction inclined groove 160 to the area of the V-shapeland portion row 100 between the side walls. Further, the sipe is closedin the ground contact surface, and therefore the area thereof is zero.

A ratio of the width direction length of the terminal inclined groove150 to the width direction length of the V-shape land portion block 101(see FIG. 10) is set in a range between 24% and 64%. The ratio ispreferably set in a range between 34% and 54%. Further, a ratio of thewidth direction length of the V-shape land portion block 101 to thetread width of the tire is set in a range between 8% and 38%. The ratiois preferably set in a range between 10% and 25%.

A ratio of the circumferential direction length of the terminal inclinedgroove 150 to the circumferential direction length of the V-shape landportion block 101 (see FIG. 10) is set in a range between 7% and 37%.The ratio is preferably set in a range between 9% and 29%. Thecircumferential direction length of the terminal inclined groove 150denotes a length of the terminal inclined groove 150 along the tirecircumferential direction (see FIG. 10). Further, the width directionlength of the terminal inclined groove 150 denotes a length of theterminal inclined groove 150 along the tire width direction (see FIG.10). Further, those are similarly applied to other grooves hereinafter.

A ratio of the circumferential direction length of the terminal inclinedgroove 150 to the width direction length of the terminal inclined groove150 is set in a range between 2.5% and 20%. The ratio is preferably setin a range between 3% and 10%.

A notched recess portion recessed to notch the V-shape land portionblock 101 is formed on the side wall 100 b located at an end in the tirewidth direction of the V-shape land portion block 101. Specifically, thenotched recess portion 170 is formed in the V-shape land portion block101.

A communication sipe (communication sipe 142) communicated with thenotched recess portion 170 is included in the sipe 140 formed in theV-shape land portion block 101.

A circumferential direction length along the tire circumferentialdirection of the notched recess portion 170 (see FIG. 10) becomes longertoward the end of the V-shape land portion block 101, specifically theside wall 100 b, in the tire width direction.

In the present embodiment, the notched recess portion 170 is formed as awedge groove having a wedge shape. However, a shape of the notchedrecess portion 170 is not limited to the wedge shape (triangle) taperedtoward the center of the V-shape land portion block 101 in the tirewidth direction in the tread surface view. For example, the notchedrecess portion 170 may be formed in a shape having the edge of thecommunication sipe 142 not formed in a sharp angle such as asemicircular shape (fan shape), and a rectangular shape having chamferedcorners in the tread surface view.

FIG. 5 is an enlarged plane view of a part of the V-shape land portionblock 101 including the communication sipe 142. As shown in FIG. 5, oneside wall (side wall 100 d), which forms the communication sipe 142, ofthe V-shape land portion block 101 is continued to one side wall (sidewall 100 e), which forms the notched recess portion 170 (wedge groove),of the V-shape land portion block 101. The side wall 100 d is extendedin the same direction as the communication sipe 142.

Further, another side wall (side wall 100 f), which forms thecommunication sipe 142, of the V-shape land portion block 101 iscontinued to another side wall (side wall 100 g), which forms the wedgegroove, of the V-shape land portion block 101. The side wall 100 g isextended in an opposite direction to the communication sipe 142 withrespect to the tire width direction, namely on the basis of the tirewidth direction.

A ratio of an area of the notched recess portion 170 to an area of theV-shape land portion block 101 including the area of the notched recessportion 170 is set in a range between 0.3% and 15%. The ratio ispreferably set in a range between 0.3% and 7%.

A ratio of the width direction length of the notched recess portion 170(see FIG. 10) to the width direction length of the V-shape land portion101 is set in a range between 9% and 38%. The ratio is preferably set ina range between 9,2% and 30%, more preferably a range between 11% and26%. Further, a ratio of the circumferential direction length of thenotched recess portion 170 to the circumferential direction length ofthe V-shape land portion block 101 is set in a range between 3% and 23%.The ratio is preferably set in a range between 3% and 13%.

Further, a ratio of the width direction length of the notched recessportion 170 to the circumferential direction length of the notchedrecess portion 170 is set in a range between 130% and 270%. The ratio ispreferably set in a range between 150% and 230%.

The notched recess portion 170 is formed in the side wall 100 b of theV-shape land portion block 101 at a side of the tread end. The notchedrecess portion 170 is recessed toward a side of the tire equatorial lineCL. The circumferential direction length of the notched recess portion170 becomes longer toward the tread end.

The V-shape land portion block 101 includes a projection portion sidewall 111 (projection portion first side wall) formed at one side in thetire width direction with respect to the most projected portion 110 a ofthe projection portion 110 and inclined against the tire widthdirection, and a projection portion side wall 112 (projection portionsecond side wall) formed at another side in the tire width directionwith respect to the most projected portion 110 a of the projectionportion 110 and inclined against the tire width direction.

The sipe 130 formed at one side in the tire width direction,specifically at a side of the tire equatorial line CL is extended in thesame direction as the projection portion side wall 111. On the otherhand, the sipe 140 formed at another side in the tire width direction,specifically at a side of the tread end is extended in the samedirection as the projection portion side wall 112.

The projection portion side wall 111 is longer than the projectionportion side wall 112. Specifically, a length along a side wall surfaceof the projection portion side wall 111 in the tread surface view islonger than a length of a side wall surface of the projection portionside wall 112 in the tread surface view. Further, the sipe 130 isshorter than the sipe 140. Specifically, a length along the extendingdirection of the sipe 130 (not including amplitude due to the zigzagportion) is shorter than a length along the extending direction of thesipe 140 (not including amplitude due to the zigzag portion).

The V-shape land portion block 101 includes a recess portion side wall121 (recess portion first side wall) formed at one side in the tirewidth direction, specifically a side of the tire equatorial line CL,with respect to the most recessed portion 120 a and inclined against thetire width direction, and a recess portion side wall 122 (recess portionsecond side wall) formed at another side in the tire width direction,specifically at a side of the tread end, with respect to the mostrecessed portion 120 a and inclined against the tire width direction.

The recess portion side wall 121 is longer than the recess portion sidewall 122. Specifically, a length along a side wall surface of the recessportion side wall 121 in the tread surface view is longer than a lengthalong a side wall surface of the recess portion side wall 122 in thetread surface view. Further, the projection portion side wall 111 islonger than the recess portion side wall 121. Further, the recessportion side wall 122 is longer than the recess portion side wall 121.Specifically, a length along a side wall surface of the recess portionside wall 122 in the tread surface view is longer than a length along aside wall surface of the recess portion side wall 121 in the treadsurface view.

In the present embodiment, an inclined angle (inclined direction) of theprojection portion side wall 111 and an inclined angle (inclineddirection) of the recess portion side wall 121 are the same (samedirection) to each other.

The most projected portion 110 a of the V-shape land portion block 101is offset in the tire width direction from the center in the tire widthdirection of the V-shape land portion block 101. An offset amount ispreferably set in a range between 2.5% and 22.5% of the width directionlength of the V-shape land portion block 101.

In a case in which the most projected portion 110 a is arranged offsetfrom the center by 2.5% to 22.5% of the width of the V-shape landportion block 101, by setting the circumferential length of the widthdirection inclined groove 160 at the side of the tread end to be smalland by setting the circumferential direction length of the V-shape landportion block 101 to be large, the block rigidity at the side of thetread end is increased. Further, by setting the circumferentialdirection length of the width direction inclined groove 160 at the sideof the tire equatorial line CL to be large and by setting thecircumferential direction length of the V-shape land portion block 101to be small, the block rigidity is decreased, and thereby the V-shapeland portion block 101 is appropriately fallen at the side of the tireequatorial line CL rather than the at the side of the tread end, and theedge effect by the block edge and the sipe edge is improved at the sideof the tire equatorial line CL. With this, the block rigidity of theV-shape land portion block 101 is balanced well, and both of the on-iceperformance and the wear resistant performance are derived.

A circumferential length W1 along the tire circumferential direction ofthe inclined groove portion 161 located at one side in the tire widthdirection with respect to the bent portion 163 is longer than acircumferential direction length W2 along the tire circumferentialdirection of the inclined groove portion 162 located at another side inthe tire width direction with respect to the bent portion 163. Thecircumferential direction length W1 and the circumferential directionlength W2 denote, similar to the circumferential direction length ofother groove portion, a length of the inclined groove portion 161 alongthe tire circumferential direction and a length of the inclined grooveportion 162 along the tire circumferential direction, respectively.

The sipe 130 formed at one side in the tire width direction,specifically at a side of the tire equatorial line CL, with respect tothe bent portion 163 is extended in the same direction as the inclinedgroove portion 161. On the other hand, the sipe 140 formed at anotherside in the tire width direction, specifically at a side of the treadend, with respect to the bent portion 163 is extended in the samedirection as the inclined groove portion 162.

Further, the sipe 140 includes a sipe wider than the sipe 130 in thetire width direction. Specifically, the sipe 140 and the communicationsipe 141 shown in FIG. 4 are wider than the sipe 130 in the tire widthdirection.

A width direction length, which is a length of the inclined grooveportion 161 in the tire width direction, is longer than a widthdirection length of the inclined groove portion 162. Further, the end131 of the sipe 130 is terminated at a side of the end, specifically ata side of the side wall 110 a in the tire width direction with respectto the most projected portion 110 a of the projection portion 110.

The circumferential direction length W1 of the inclined groove portion161 is set in a range between 1.32 times and 2.17 times as large as thecircumferential direction length W2 of the inclined groove portion 162.The length W1 is preferably set in a range between 1.64 times and 1.96times as large as the length W2.

A ratio of an area of the width direction inclined groove 160 to an areaof the V-shape land portion block 101 is set in a range between 10% and40%. The ratio is preferably set in a range between 12% and 32%.Further, a ratio of an area of the V-shape land portion block 101 to theground contact area of the pneumatic tire 10 is set in a range between10% and 31%. The ratio is preferably set in a range between 9% and 12%.

A ratio of the width direction length of the inclined groove portion 161to a width (length between the side wall 100 a and the side wall 100 b)of the V-shape land portion block 101 in the tire width direction is setin a range between 50% and 78%. The ratio is preferably set in a rangebetween 52% and 68%.

Further, the circumferential direction length of the inclined grooveportion 161 is preferably set in a range, for example, between 2.7 mmand 6.1 mm. The circumferential direction length of the inclined grooveportion 162 is preferably set in a range, for example, between 1.4 mmand 3.9 mm.

(2.2) Center Land Portion Row 200

FIG. 6 is an enlarged plane view of a part of the center land portionrow 200. The center land portion row 200 is a compound land portion rowformed by a land portion row 201 (first land portion row) and a landportion row 202 (second land portion row) arranged along the tirecircumferential direction. The land portion row 201 and the land portionrow 202 are arranged adjacent to each other in the tire width direction.

In the present embodiment, the land portion row 201 is arranged closerto the tire equatorial line CL than the land portion row 202. Further,at least a part of the center land portion row 200 is formed in thecenter region including the tire equatorial line CL. Here, thedefinition of the center region is as described above.

The land portion row 201 is formed by a plurality of land portion blocks201 (first land portion block) arranged along the tire circumferentialdirection. Further, the land portion row 202 is formed by a plurality ofland portion blocks 260 (second portion land portion block) arrangedalong the tire circumferential direction.

A terminal inclined groove 220 (first terminal inclined groove) inclinedagainst the tire width direction and opened to a side wall 210 a at aside of the land portion row 202 is formed in the land portion block210. Further, a notched groove 240 having a wedge shape opened to a sidewall 210 b opposite to the land portion row 202 is formed in the landportion block 210. Here, the notched groove 240 is not limited to awedge shape, and therefore the notched groove 240 may be formed in ashape tapered toward a distal end of the notched groove 240.

One end of the terminal inclined groove 220, specifically an end 221, isterminated in the land portion block 210. Further, a distal end 241 ofthe notched groove 240 is also terminated in the land portion block 210.

A crossing inclined groove is formed between the land portion blocks 260adjacent to each other to separate the land portion blocks 260.Specifically, a crossing inclined groove 270 is formed between the landportion blocks 260 adjacent to each other.

The crossing inclined groove 270 is inclined in the same direction asthe terminal inclined groove 220. That is, an extending direction of thecrossing inclined groove 270 and an extending direction of the terminalinclined groove 220 are the same direction in the tread surface view.

A plurality of sipes 230 inclined against the tire width direction toextend in a direction different from the extending direction of thecrossing inclined groove 270 is formed in the land portion block 210. Aplurality of sipes 290 inclined against the tire width direction toextend in a direction different from the extending direction of thecrossing inclined groove 270 is formed in the land portion block 260. Inthe present embodiment, each of the sipe 230 and the sipe 290 is formedin a zigzag shape in the tread surface view.

The terminal inclined groove 220 and the notched groove 240 are locatedon an extension line of the crossing inclined groove 270.

A terminal inclined groove 280 (second terminal inclined groove)inclined in the same direction as the terminal inclined groove 220 andopened to a side wall opposite to the first land portion row is formedin the land portion block 260. One end of the terminal inclined groove280, specifically an end 281, is terminated in the land portion block260.

A communication sipe 231 communicated with the terminal inclined groove220 is included in the sipe 230. One end of the communication sipe 231is communicated with a terminal portion (end 221) of the terminalinclined groove 220. On the other hand, another end of the communicationsipe 231 is opened to a side wall 210 b opposite to the land portion row202.

The terminal inclined groove 220 and the crossing inclined groove 270are inclined in opposite directions to the sipe 230 and the sipe 290against the tire width direction, respectively.

The crossing inclined groove 270 is provided with a first groove widthportion 271 (first groove portion) having a circumferential length(groove width) as same as that of the terminal inclined groove 220, anda second groove width portion 272 (second groove portion) having acircumferential length (groove width) larger than that of the firstgroove width portion 271. The first groove width portion 271 is formedat a side of the land portion block 210.

Further, a hook-shaped groove is formed at an end of the crossinginclined groove 270 opposite to the land portion row 201. Specifically,a hook-shaped groove portion 273 is formed at the end of the crossinginclined groove 270. The hook-shaped groove portion 273 is inclined inthe same direction as the sipe 290 and inclined in an opposite directionto the terminal inclined groove 280 on the basis of the tire widthdirection. The hook-shaped groove portion 273 is communicated with thesecond groove width portion 272.

Further, a circumferential direction groove 60 (in-row circumferentialdirection groove) extended in the tire circumferential direction isformed between the land portion row 201 and the land portion row 202.The circumferential direction groove 60 is not extended in a linearmanner in the tire circumferential direction. The circumferentialdirection groove 60 is provided with a circumferential direction grooveportion and an inclined lug groove portion.

Specifically, the circumferential direction groove 60 is provided with acircumferential direction groove portion 61 extended in the tirecircumferential direction and inclined against the tire circumferentialdirection, and an inclined lug groove portion 62 communicated with thecircumferential direction groove portion 61 adjacent to the inclined luggroove portion 62 in the tire circumferential direction. The inclinedlug groove portion 62 is extended in the tire width direction andinclined in the same direction as the terminal inclined groove 220against the tire width direction.

Side walls located at ends in the tire circumferential direction of theland portion block 210, specifically side walls 210 c, 210 d areinclined against the tire width direction. Similarly, side walls locatedat ends in the tire circumferential direction of the land portion block260, specifically side walls 220 c, 220 d are also inclined against thetire width direction.

Further, the side walls are inclined in the opposite direction to thesipe 230 and the sipe 290 against the tire width direction, namely onthe basis of the tire width direction. Further, an inclined angle ofeach of the sipe 230 and the sipe 290 against the tire width directionis larger than an inclined angle of the side wall (side walls 210 c, 210d, 220 c, 220 d) against the tire width direction.

Specifically, the inclined angle of each of the sipe 230 and the sipe290 is set in a range between 9 degrees and 39 degrees. The inclinedangle is preferably set in a range between 12 degrees and 24 degrees.Further, the inclined angle of the side wall (side walls 210 c, 210 d,220 c, 220 d) is set in a range between 6 degrees and 36 degrees. Theinclined angle is preferably set in a range between 11 degrees and 31degrees.

An extending direction of the crossing inclined groove 270 is inclinedin a different direction to the sipe 230 and the sipe 290 against thetire width direction. Specifically, in the tread surface view, theextending direction of the extension line of the crossing inclinedgroove 270 is inclined upward to the right. On the other hand, theextending direction of each of the sipe 230 and the sipe 290 is inclinedupward to the left.

As a groove total area S1 is defined by a total area of the terminalinclined groove 220, the terminal inclined groove 280 and the crossinginclined groove 270 in the ground contact surface of the pneumatic tire10 with the road surface, and a compound land portion row total area S2is defined by a total area of the land portion and the groove portionbetween one end in the tire width direction of the center land portionrow 200 and another end in the tire width direction of the center landportion row 200, a ratio S1/S2 is set in a range between 0.05 and 0.25.Further, the value of S1/S2 is preferably set in a range between 0.05and 0.15.

Further, an interval in the circumferential direction of the sipes 230adjacent to each other in the land portion block 210 is set in a rangebetween 3.3 mm and 10.0 mm. The sipe interval is preferably set in arange between 3.7 mm and 5.6 mm. Further, an interval in thecircumferential direction of the sipes 290 adjacent to each other in theland portion block 260 is set in a range between 4.4 mm and 10.0 mm. Thesipe interval is preferably set in a range between 5.5 mm and 8.3 mm.

The interval in the circumferential direction of the sipes 230 denotes“sipe interval” shown in FIG. 11, which is an interval (length) betweenthe sipes 230 adjacent to each other and intersected with a straightline parallel to the tire circumferential direction.

A negative ratio of the land portion block 210 is set in a range between8.9% and 20.7%. The negative ratio is preferably set in a range between11.8% and 17.8%. Further, a negative ratio of the land portion block 260is set in a range between 11.8% and 27.4%. The negative ratio ispreferably set in a range between 15.7% and 23.5%.

Further, an average negative ratio of the land portion block 210 and theland portion block 260 adjacent to the land portion block 210 is set ina range between 13.2% and 30.8%. The negative ratio is preferably set ina range between 17.6% and 26.4%.

The negative ratio of the land portion block 210 denotes a ratio(percentage) of the total area of the terminal inclined groove 220 andthe notched groove 240 to the total area of the land portion (notincluding the sipe closed when in the ground contact) of the landportion block 210, and the terminal inclined groove 220 and the notchedgroove 240 formed in the land portion block 210. Further, the negativeratio of the land portion block 260 denotes a ratio of an area of theterminal inclined groove 280 to the total area of the land portion (notincluding the sipe closed when in the ground contact) of the landportion block 260, and the terminal inclined groove 280 formed in theland portion block 260.

In the present embodiment, the inclined angle of the sipe 290 againstthe tire width direction, and the inclined angles of the terminalinclined groove 220, the second terminal inclined groove and thecrossing inclined groove 270 against the tire width direction are largerthan the inclined angle of the sipe 230 and the inclined angle of theterminal inclined groove 220 against the tire width direction in theland portion block 210.

Further, the terminal inclined groove 220, the second terminal inclinedgroove and the crossing inclined groove 270 are inclined against thetire width direction in an opposite direction to the sipe 230 and thesipe 290.

FIGS. 7A and 7B are a view for describing rotation moment generated inthe land portion block 210, and a view for describing rotation momentgenerated in the land portion block 210P in a conventionalconfiguration, respectively.

As shown in FIGS. 7A and 7B, force in a vector direction along the sidewall of the tire circumferential direction end is not for rotating theland portion block 210 and the land portion block 210P, however input ina vector direction perpendicular to the side wall of the tirecircumferential direction end generates moment to rotate the landportion blocks (counterclockwise direction in FIGS. 7A and 7B).

In the land portion block 210, when the input in the tirecircumferential direction is applied, the rotation moment generated at aside wall position of the tire circumferential direction end of the landportion block 210 and the rotation moment generated at a position of thesipe 230 are opposite direction to each other, and therefore therotation moments are cancelled to each other, so that the deformation ofthe land portion block 210 is suppressed.

(2.3) Shoulder Land Portion Row 300 in and Shoulder Land Portion Row300out

FIG. 8 is an enlarged plane view of a part of the shoulder land portionrow 300 in. FIG. 9 is an enlarged perspective view of a land portionblock 310 that forms the land portion block 310 in.

The shoulder land portion row 300 in and the shoulder land portion row300 out are formed symmetry with respect to the tire equatorial line CL.Hereinafter, a shape of the shoulder land portion row 300 in will bedescribed.

The land portion block 310 that forms the shoulder land portion row 300in is formed as a land portion block defined by the circumferentialdirection groove 50 and the lug groove 70. In the present embodiment,the land portion block 310 is formed at a tread end including a groundcontact end with the road surface in the tire width direction.

A circumferential direction sipe 320 having a zigzag shape extended inthe tire circumferential direction, a width direction sipe 330(equatorial side width direction sipe) having a zigzag shape extended inthe tire width direction, and a width direction sipe 340 (tread end sidewidth direction sipe) are formed in the land portion block 310.

The width direction sipe 330 is located at a side of the tire equatorialline CL with respect to the circumferential direction sipe 320. Thewidth direction sipe 340 is located at a side of the tread end in thetire width direction with respect to the circumferential direction sipe320.

The circumferential direction sipe having a zigzag shape extended in thetire circumferential direction denotes a sipe having an extendingdirection on the tread surface as same as the tire circumferentialdirection and bent in a zigzag shape in the extending direction. A widthdirection sipe having a zigzag shape extended in the tire widthdirection denotes a sipe having an extending direction on the treadsurface as same as the tire width direction and bent in a zigzag shapein the extending direction.

In the land portion block 310, a ratio L1/L2 of a total amount L1 of awidth direction edge component, which is an edge component in the tirewidth direction of the circumferential direction sipe 320, to a totalamount L2 of a circumferential direction edge component, which is anedge component in the tire circumferential direction of the widthdirection sipe 320 and the width direction sipe 340, is set in a rangebetween 16.0% and 37.4%. The ratio L1/L2 is preferably set in a rangebetween 21.4% and 32.0%.

Here, the edge component derives an edge effect that works in aorthogonal direction to an input direction from the road surface to thegroove or the sipe of the pneumatic tire 10, when the pneumatic tire 10scratches the road surface by the groove or the sipe. The edge componentdenotes a size (length) of the sipe in an orthogonal direction to theinput direction from the road surface.

The edge component of one width direction sipe in the land portion blockdenotes a length of the sipe projected on a straight line inclinedagainst the tire equatorial line CL by 90 degrees, namely a straightline parallel to the tire width direction, regardless of the widthdirection sipe linearly extended on the tread surface, or the widthdirection sipe having amplitude such as a zigzag wave.

Further, the edge component denotes a so-called circumferentialdirection edge component along the tire width direction of the landportion block in which force is applied in the tire circumferentialdirection unless otherwise mentioned as described above. The edgecomponent includes a block edge component of the edge of the block, asipe edge component of the edge of the sipe and the like.

Further, a ratio (L1+L2)/L3 of a sum of the total amount L1 and thetotal amount L2 to an average length L3 in the tire circumferentialdirection of the land portion block 310 is set in a range between 3.4and 7.8. The ratio is preferably set in a range between 3.9 and 5.9. Ina case in which a plurality of the circumferential direction lengths ofthe land portion blocks 310 formed along the tire circumferentialdirection exists, namely in a case in which the shoulder land portionrow 300 in has a plurality of pitches, the average length L3 denotes anaverage of the circumferential direction lengths of the land portionblocks 310.

In the present embodiment, a repeating period T of the zigzag shape ofthe circumferential direction sipe 320 is equal to an interval h of thewidth direction sipes 340 adjacent to each other in the tirecircumferential direction. Further, the period T may be smaller than theinterval h.

Further, width direction amplitude (amplitude A1), which is theamplitude in the tire width direction of the circumferential directionsipe 320, is larger than circumferential amplitude (amplitude A2, A3),which is the amplitude in the tire circumferential direction of thewidth direction sipe 340.

A circumferential direction sub sipe extended in the tirecircumferential direction is formed in the land portion block 310.Specifically, a circumferential direction linear sipe 351 having alinear shape, and a circumferential direction linear sipe 352 having alinear shape are formed in the land portion block 310. Here, thecircumferential direction sub sipe may not be formed in a linear shapesuch as the circumferential direction linear sipe 351 and thecircumferential direction linear sipe 352, and therefore thecircumferential direction sub sipe may include one bent portion having asmall bent angle.

One ends of the circumferential direction linear sipe 351 and thecircumferential direction linear sipe 352 are communicated with thewidth direction sipe 340. On the other hand, another ends of thecircumferential direction linear sipe 351 and the circumferentialdirection linear sipe 352 are opened to the side walls 310 a, 310 blocated at a side of the tire circumferential direction end of the landportion block 310, respectively.

The circumferential direction sipe 320 includes a linear portionlinearly extended to be parallel to the tire circumferential direction.Specifically, the circumferential direction sipe 320 includes a linearportion 321 and a linear portion 322.

The linear portion 321 and the linear portion 322 are formed at the endof the land portion block 310 in the tire circumferential direction.Specifically, the linear portion 321 is formed at a side of the sidewall 310 a at the tire circumferential end of the land portion block310, and the linear portion 322 is formed at a side of the side wall 310b.

Each of the linear portion 321 and the linear portion 322 is formed at aposition offset from a center position CT of the amplitude A1 in thetire width direction of the circumferential direction sipe 320. That is,each of the linear portion 321 and the linear portion 322 is formed at aposition shifted from the center position CT in the tire widthdirection.

An end 332 at a side of the tread end of the width direction sipe 330 iscommunicated with the circumferential direction sipe 320. On the otherhand, an end 341 at a side of the tire equatorial line CL of the widthdirection sipe 340 is not communicated with the circumferentialdirection sipe 320 but terminated in the land portion block 310 at aside of the tread end with respect to the circumferential direction sipe320.

Further, an end 331 at a side of the tire equatorial line CL of thewidth direction sipe 330 is communicated with the circumferentialdirection groove adjacent to the land portion block 310, specificallythe circumferential direction groove 50 formed at a side of the tireequatorial line CL. On the other hand, an end 341 at a side of the treadend of the width direction sipe 340 is terminated in the land portionblock 310.

Further, an end 332 at a side of the tread end of the width directionsipe 330 is communicated with an apex 323 of the circumferentialdirection sipe 320 having a zigzag shape. The width direction sipe 340is located on an extension line of the width direction sipe 330communicated with the apex 323 of the circumferential direction sipe 320having a zigzag shape.

The circumferential direction sipe 320 has predetermined amplitude(amplitude A1) in the tire width direction. The end 341 of the widthdirection sipe 340 is located in a range of the amplitude A1.

A notched step portion notching the land portion block 310 is formed inthe side wall 310 b located at a side of the tire circumferentialdirection end of the land portion block 310. Specifically, a stepportion 360 is formed at the end of the land portion block 310 at theside of the tread end in the tire width direction.

The step portion 360 is formed only in one side wall of the land portionblock 310 at the side of the tire circumferential direction end,specifically only in the side wall 310 b.

As shown in FIG. 9, the step portion 360 is provided with a raisedbottom surface located at an outer side in the tire radial directionwith respect to a groove bottom 70 b of the lug groove 70. Specifically,the step portion 360 is provided with a raised bottom surface 361 havinga rectangular shape extended in the tire width direction.

In the present embodiment, the raised bottom surface 361 is inclinedagainst the tire radial direction in a tire side view. A position in thetire radial direction of the raised bottom surface 361 is not especiallylimited, however the position is preferably set in a range between 25%and 50% of a height (length in the tire radial direction) of the landportion block 310 from a viewpoint of securing the block rigidity of theland portion block 310.

One end of the circumferential direction linear sipe 352, specificallyan end 352 a at a side of the side wall 310 b is opened to the side wall310 b of the tire circumferential direction end at a side of the stepportion 360 of the land portion block 310. That is, the end 352 a isopened to an end 362 at a side of the tire equatorial line CL of thestep portion 360. On the other hand, another end of the circumferentialdirection linear sipe 352, specifically an end 352 b at a side of thewidth direction sipe 340 is communicated with the width direction sipe340.

The raised bottom surface 361 is inclined such that the height in thetire radial direction becomes lower toward the tire circumferential endof the land portion 310, namely the side wall 310 b.

A zigzag surface having predetermined amplitude in the tirecircumferential direction is formed in the side wall at a side of thetire circumferential direction end of the land portion 310.Specifically, a zigzag surface 380 is formed in each of the side wall310 a and the side wall 310 b. The zigzag surface 380 is formed at theend at a side of the tire equatorial line CL of each of the side wall310 a and the side wall 310 b. A shape of the zigzag surface 380 is thesame as the shape of the width direction sipe 340 in the tread surfaceview.

(3) Relation Between Pitch and Sipe of Land Portion Block in thePneumatic Tire 10

Next, a relation between a pitch and a sipe in the pneumatic tire 10will be further described with reference to FIG. 10 through FIG. 13.

FIG. 10 is a view illustrating definitions of respective lengths in theV-shape land portion row 100. FIG. 11 is a view illustrating definitionsof respective lengths in the center land portion row 200. FIG. 12 is aview illustrating definitions of respective lengths in the shoulder landportion row 300 in. FIG. 13 is a plane developed view of a part of apneumatic tire 10A having a pitch different from that of the pneumatictire 10 shown in FIG. 1 through FIG. 12.

As described above, one or more sipes extended in the tire widthdirection are formed in at least one of the land portion blocks of thepneumatic tire 10 (and the pneumatic tire 10A, hereinafter the same).

As an average sipe interval h is defined by an average interval of thesipes adjacent to each other in the tire circumferential direction andan average pitch length L is defined by an average length of a repeatingunit of the land portion blocks in the tire circumferential direction,it is preferable to fulfill the following relation.

0.130≤(h/L)≤0.400

Here, the value of (h/L) is more preferably set in a range between 0.137and 0.197, and further more preferably set in a range between 0.144 and0.19.

The average sipe interval h (unit mm) denotes an average circumferentialdirection length of the sipes adjacent to each other in the tirecircumferential direction in the land portion block. In a case in whichthe sipes adjacent to each other do not exist, the average sipe intervalh is defined by the circumferential direction length between the tirecircumferential direction end of the land portion block and the sipe.

Further, in a case in which the sipe is not formed at all (the number ofthe sipes is zero), the average sipe interval h is defined by thecircumferential direction length between one tire circumferentialdirection end of the land portion block and another tire circumferentialdirection end. Normally, the land portion block is divided substantiallyevenly in the tire circumferential direction by the sipe, however theland portion block may not be divided evenly. Here, the average sipeinterval h denotes an average value in all land portion blocks formed inthe circumference of the land portion block row unless otherwisementioned.

Further, the pitch denotes one basic unit of a tread pattern formed by apattern repeated continuously in the tire circumferential direction atone or more kinds of lengths. The average pitch length L (unit mm)denotes a length of the pitch in the tire circumferential direction. Theaverage pitch length L denotes an average circumferential directionlength of the pitches in the land portion block row unless otherwisementioned.

Further, it is preferable that the average sipe interval h and theaverage pitch length L fulfill the following relation.

140 (mm)²≤(h×L)≤350 (mm)² (hereinafter, unit (mm)² is omitted)

Here, the value of (h×L) is more preferably set in a range between 148and 250, and further more preferably set in a range between 150 and 220.

The average sipe interval h of the center portion land portion blockpreferably fulfills a relation of 3.0 mm≤h≤7.1 mm. Further, the averagesipe interval h of the center portion land portion block more preferablyfulfills a relation of 3.5 mm≤h≤6.6 mm, and further more preferablyfulfills a relation of 3.7 mm≤h≤5.6 mm.

The average sipe interval h of the second portion land portion blockpreferably fulfills a relation of 3.3 mm≤h≤7.7 mm. Further, the averagesipe interval h of the second portion land portion block more preferablyfulfills a relation of 3.8 mm≤h≤7.2, mm and further more preferablyfulfills a relation of 4.1 mm≤h≤6.1 mm.

The average sipe interval h of the shoulder portion land portion blockpreferably fulfills a relation of 3.7 mm≤h≤8.5 mm. Further, the averagesipe interval h of the shoulder portion land portion block morepreferably fulfills a relation of 4.2 mm≤h≤8.0 mm, and further morepreferably fulfills a relation of 4.5 mm≤h≤6.8 mm.

Here, the definitions of the center portion, the second portion and theshoulder portion are as described above.

A plurality of the sipes extended in the tire width direction is formedin the land portion block of the pneumatic tire 10 according to thepresent embodiment. In this case, the average sipe interval h preferablyfulfills a relation of 3.4 mm≤h≤7.9 mm. Further, in this case, theaverage sipe interval h more preferably fulfills a relation of 3.9mm≤h≤7.4 mm, and further more preferably fulfills a relation of 4.2mm≤h≤6.3 mm.

Further, in this case, the average pitch length L preferably fulfills arelation of 19.2 mm≤L≤44.6 mm. Further, the average pitch length L morepreferably fulfills a relation of 22.0 mm≤L≤41.6 mm, and further morepreferably fulfills a relation of 23.6 mm≤L≤35.4 mm.

Further, as an average block edge component Dball is defined by anaverage of the edge components of all land portion blocks against thetire circumferential direction, an average sipe edge component Dsall isdefined by an average of the edge components of all sipes against thetire circumferential direction, and an average block rigidity G isdefined by an average of the rigidity of all land portions, it ispreferable to fulfill the following relation.

2.20 (mm)³ /N≤(Dball/Dsall)/G≤4.00 (mm)³ /N (hereinafter, unit (mm)³ /Nis omitted)

Here, the definition of the edge component is as described above.Further, the block rigidity as a base of the average block rigidity G isa value when the shearing deformation in the tire circumferentialdirection is applied. Specifically, the block rigidity per unit area iscalculated by the following formula.

Shearing stress (N/mm)/Land portion block ground contact area (mm²)

In particular, the measurement using the Amsler testing machine asdisclosed in JP 4615983 B is calculated by FEM.

Further, as a value of R is defined by a value of (Dball/Dsall)/G, it ismore preferable to fulfill a relation of 2.55≤(R₂/Rc)≤3.55, and it isfurther more preferable to fulfill a relation of 2.80≤(R₂/Rc)≤3.20.

As a value of Rc is defined by a value of (Dballc/Dsallc)/Gc of thecenter portion land portion block and a value of R₂ is defined by avalue of (Dball₂/Dsall₂)/G₂ of the second portion land portion block, itis preferable to fulfill the following relations.

2.20≤(Dball/Dsall)/G≤4.00

1.10≤(R ₂ /Rc)≤5.88

Here, it is more preferable to fulfill a relation of 1.10≤(R₂/Rc)≤3.55,and it is further more preferable to fulfill a relation of1.20≤(R₂/Rc)≤1.80.

Further, as a value of R₂ is defined by a value of (Dball₂/Dsall₂)/G₂ ofthe second portion land portion block, and a value of Rs is defined by avalue of (Dballs/Dsalls)/Gs of the shoulder portion land portion block,it is preferable to fulfill the following relation.

1.10≤(Rs/R ₂)≤2.90

Here, it is more preferable to fulfill a relation of 1.10≤(Rs/R₂)≤2.35,and it is further more preferable to fulfill a relation of1.20≤(Rs/R₂)≤1.80.

Further, as an average block edge component Dball is defined by anaverage of the edge components of all land portion blocks against thetire circumferential direction, and an average sipe edge component Dsallis defined by an average of the edge components of all sipes against thetire circumferential direction, it is preferable to fulfill thefollowing relation.

0.15≤(Dball/Dsall)≤0.48

Here, it is more preferable to fulfill a relation of0.21≤(Dball/Dsall)≤0.31, and it is further more preferable to fulfill arelation of 0.23≤(Dball/Dsall)≤0.29.

Further, as a value of Pc is defined by a value of (Dballc/Dsallc) ofthe center portion land portion block, and a value of P₂ is defined by avalue of (Dball₂/Dsall₂) of the second portion land portion block, it ispreferable to fulfill the following relation.

1.12≤(P ₂ /Pc)≤5.88

Here, it is more preferable to fulfill a relation of 1.15≤(P₂/Pc)≤4.00,and it is further more preferable to fulfill a relation of1.17≤(P₂/Pc)≤2.50.

Further, as a value of Pc is defined by a value of (Dballc/Dsallc) ofthe center portion land portion block, a value of P₂ is defined by avalue of (Dball₂/Dsall₂) of the second portion land portion block, and avalue of Ps is defined by a value of (Dballs/Dsalls) of the shoulderportion land portion block, it is preferable to fulfill the followingrelation.

0.81≤{(Ps/P ₂)/(P ₂ /Pc)}≤3.70

Here, it is more preferable to fulfill a relation of0.94≤{(Ps/P₂)/(P₂/Pc)}≤3.00, and it is further more preferable tofulfill a relation of 0.96≤{(Ps/P₂)/(P₂/Pc)}≤2.80.

Further, as a value of hc is defined by an average sipe interval, whichis an average interval of the sipes adjacent to each other, in the tirecircumferential direction in the center portion land portion block, anda value of h₂ is defined by an average sipe interval in the second landportion block, it is preferable to fulfill the following relation.

1.00≤(h ₂ /hc)≤7.00

Here, it is more preferable to fulfill a relation of 1.05≤(h₂/hc)≤4.00,and it is further more preferable to fulfill a relation of1.09≤(h₂/hc)≤2.00.

Further, as a value of hs is defined by an average sipe interval in theshoulder portion land portion block, it is preferable to fulfill thefollowing relation.

1.05≤(hs/hc)≤4.00

Here, it is more preferable to fulfill a relation of 1.05≤(hs/hc)≤3.00,and it is further more preferable to fulfill a relation of1.10≤(hs/hc)≤1.79.

Further, it is preferable to fulfill the following relation.

0.97≤(hs/h ₂)≤2.15

Here, it is more preferable to fulfill a relation of 0.97≤(hs/h₂)≤1.71,and it is further more preferable to fulfill a relation of1.05≤(hs/h₂)≤1.27.

(4) Functions and Effects

Next, functions and effects of the pneumatic tire 10 described abovewill be described. Specifically, functions and effects of a whole of thepneumatic tire 10, and functions and effects of the V-shape land portionrow 100, the center land portion row 200, the shoulder land portion row300 in, and the shoulder land portion row 300 out will be described.

(4.1) V-Shape Land Portion Row 100

The V-shape land portion block 101 is provided with the projectionportion 110 on one side wall in the tire circumferential direction, andthe recess portion 120 on another side wall. The inclined angles of theboth side walls are the same to each other. The inclined angle of theinner sipes 130, 140 in the V-shape land portion block 101 or theterminal inclined groove 150 is the same as the inclined angle of theside walls. Thus, since the most projected portion 110 a (centerportion) including the apex of the projection portion 110 has the bentportion, the rigidity of the center portion becomes high and therigidity of the whole of the V-shape land portion block 101 becomeshigh, compared to a land portion block formed in a rectangular shapewithout a bent portion. Consequently, the falling of the V-shape landportion block 101 and the lift off the road surface are suppressed, andtherefore the ground contact area is increased.

Further, both side ends in the tire width direction of the V-shape landportion block 101 are low in the block rigidity compared to the centerportion, and therefore the both end portions are deformed largely in thetire circumferential direction against the input in the tirecircumferential direction in braking. Accordingly, the edge effect isimproved.

Conventionally, in the V-shape land portion, the rigidity is improved inthe center portion, and therefore the ground contact area of the centerportion is secured by setting the width direction length of the V-shapeland portion block to be longer than the circumferential directionthereof, and the length of the edge against the tire circumferentialdirection is made long by setting the width direction lengths of theboth end portions to be long. Further, the edge effect by the block edgeand the sipe edge is improved by setting the circumferential directionlength of the V-shape land portion block to be small so as to arrangethe V-shape land portion block in the tread as many as possible whiledeforming the V-shape land portion block appropriately to such an extentin which the ground contact area can be secured.

In the present embodiment, the circumferential direction length of theV-shape land portion block 101 is longer than the width direction lengthof the V-shape land portion block 101. Thus, the block rigidity in thetire circumferential direction of the V-shape land portion block 101becomes high. Since the block rigidity in the tire circumferentialdirection of the V-shape land portion block 101 becomes high, the blockrigidity in the tire circumferential direction of the center portion inthe tire width direction becomes high, and the block rigidity in thetire circumferential direction of the both end portions in the tirewidth direction also becomes high. Further, the center portion is set tobe high in the block rigidity against the both end portions.

Further, in the center portion of the V-shape land portion block 101,the ground contact area is further increased and the block rigidity isincreased, and therefore the block edge and the sipe edge are pressedstrongly against the road surface, so that the edge effect is alsoimproved. In the both end portions of the V-shape land portion, largedeformation is suppressed, and therefore the ground contact area isincreased. Consequently, the edge effect by being pressed stronglyagainst the road surface due to the increase of the block rigidity isimproved instead of the edge effect by the deformation. Further, thewear resistant performance is improved by the increase of the blockrigidity.

With this, the falling of the V-shape land portion block 101, inparticular the falling in the tire circumferential direction, in brakingof the vehicle to which the pneumatic tire 10 is mounted can besuppressed, and the wear of the V-shape land portion can be effectivelysuppressed. Further, the circumferential direction length of the V-shapeland portion block 101 may be the same as the width direction lengththereof from a viewpoint of the derived effect. It is because the effectcan be derived unless the width direction length of the land portionblock is set to be longer than the circumferential direction lengththereof as the conventional one.

Further, in the V-shape land portion block 101, the rigidity in the tirecircumferential direction is high in both of the center portion and theboth end portions, and therefore the ground contact area of the V-shapeland portion block 101 in braking in largely increased.

In the V-shape land portion block 101, the inclined angle θ1 of theprojection portion side wall 111 (112) against the tire width directionis the same as the inclined angle θ2 of the recess portion side wall 121(122) against the tire width direction. Further, the inclined angle θ5of the sipe 130 and the terminal inclined groove 150 against the tirewidth direction is the same as the inclined angle θ1 (inclined angle θ2) of the projection portion side wall 111 (recess portion side wall 121)against the tire width direction.

Accordingly, the rotation directions of the moments generated in theprojection portion side wall 111 (112) and the sipe 130 (140) of theV-shape land portion block 101 are the same direction to each other, andtherefore the edge effects by the block edge and the sipe edge arederived in the same direction. With this, the scratching performance ona road surface by the block edge component due to the shape of theV-shape land portion block 101 and by the sipe edge component due to thesipe 130 can be improved.

Further, the end 131 of the sipe 130 and the end 151 of the terminalinclined groove 150 are terminated in the V-shape land portion block101. Further, the side wall 100 c of the V-shape land portion block 101that forms the end 151 of the terminated inclined groove 150 iscontinued to the communication sipe 141 on the extension line of thecommunication sipe 141.

Accordingly, compared to a configuration in which the V-shape landportion block 101 is divided from one end to another end by the sipe orthe inclined groove, the circumferential direction length of the V-shapeland portion block 101 can be made longer than the width directionthereof. With this, as described above, the block rigidity of theV-shape land portion block 101 becomes high, and the ground contact areais increased, and the block edge and the sipe edge due to the blockrigidity is increased. Consequently, according to the V-shape landportion row 100, the on-ice performance can be improved and the wearresistant performance can be improved.

In the V-shape land portion row 100, in order to avoid a decrease of theblock edge and the sipe edge due to the deterioration of the blockrigidity, the inclined groove (terminal inclined groove 150) isterminated, and a part of the inclined groove is replaced with thecommunication sipe 141. In a case in which the V-shape land portionblock 101 is divided from one end to another end by the inclined groove,the circumferential direction length of the land portion block becomessmaller than the width direction length thereof, and therefore the blockrigidity is deteriorated and the ground contact area is decreased.

The sipe as the communication sipe 141 is communicated with the terminalinclined groove 150. However, a portion where the communication sipe 141exists is originally formed to generate the block edge by dividing usingthe inclined groove. Thus, the reason that the inclined groove isreplaced with the sipe is to avoid the decrease of the edge as much aspossible by forming the sipe while avoiding the deterioration of theblock rigidity.

Further, the V-shape land portion block 101 is divided by the terminalinclined groove 150 and the communication sipe 141, and therefore theblock rigidity thereof is lower than a portion continued without beingdivided. Thus, in a case in which the sipes are separated withoutcommunicating the sipe with the terminal inclined groove 150, the blockrigidity of only a portion of the V-shape land portion block 101 wherethe sipes are separated becomes high, and therefore the rigiditydifference is generated because a distribution of the block rigidity inthe tire width direction of the V-shape land portion block 101 is notgently changed.

In the V-shape land portion block 101, by communicating thecommunication sipe 141 and the terminal inclined groove 150 with eachother, the block rigidity of the V-shape land portion block 101 islargely improved compared to a configuration in which the inclinedgroove crosses the V-shape land portion block 101. With this, the groundcontact area can be increased, and the edge effect can be improved.Consequently, the on-ice performance can be improved and the wearresistant performance can be improved.

In the V-shape land portion row 100, the communication sipe 142communicated with the notched recess portion 170 is formed, and thewidth in the tire circumferential direction of the notched recessportion 170 becomes larger toward the side wall 100 b of the V-shapeland portion block 101. Accordingly, the block edge component of theV-shape land portion block 101 is increased by the notched recessportion 170.

Further, in the present embodiment, by forming the notched recessportion 170 formed as a wedge groove having a wedge shape (triangularshape), the block rigidity of a portion having a sharp angle between asipe opening edge of the V-shape land portion block 101 near the openingedge of the communication sipe 142 and the side wall of the V-shape landportion block 101, becomes high although the block rigidity of theportion is originally low, compared to a configuration in which thecommunication sipe 142 is merely opened to the side wall 100 b.

Accordingly, the force pressing the communication sipe 142 against theroad surface becomes large, and therefore the edge effect of the sipeedge is improved. Further, when the block rigidity becomes high asdescribed above, the sipe formed part can be prevented from being turnedover to be lifted off the road surface in braking and therefore the wearresistant performance can be prevented from being deteriorated.

Generally, in a winter tire, a ground contact length near the tireequatorial line is long and a ground contact length at an outer side inthe tire width direction is short. Thus, in the land portion block, byintentionally increasing the sipe edge and the block edge against thetire circumferential direction in a portion near the tire equatorialline having a long ground contact length, the block rigidity of aportion at the outer side in the tire width direction is secured whileimproving the edge effect.

Thus, in order to increase the block edge, the side wall at the tirecircumferential direction end of the V-shape land portion block is madelong near the tire equatorial line and is made short at the outer sidein the tire width direction. However, if the sipe is formed in a similarway, the block rigidity of the V-shape land portion block at a side ofthe tire equatorial line is excessively decreased, and thereby rigiditybalance of the V-shape land portion block in the tire width direction isdeteriorated.

That is, the sipe 130 having a short length is formed at a side of theprojection portion side wall 111 having a long length, and the sipe 140having a long length is formed at a side of the projection portion sidewall 112 having a short length, however if this configuration is formedin an opposite way, the rigidity balance of the V-shape land portion row100 in the tire width direction is largely deteriorated.

In the V-shape land portion block 101, the sipe 130 having a shortlength is formed near the tire equatorial line, and the sipe 140 havinga long length is formed at the outer side in the tire width direction,and thereby the block rigidity in the tire width direction is balanced,and the block rigidity at a side of the tire equatorial line CL issecured.

Further, by setting the sipe 140 at the outer side in the tire widthdirection to be long, the block rigidity is increased by the bentportion (projection portion 110 and recess portion 120), and the sipeedge is increased. Further, since the block rigidity at the outer sidein the tire width direction becomes high, the force pressing the V-shapeland portion block 101 including the sipe 140 against the road surfacebecomes large and therefore the sipe edge is increased. Further,contrary to the conventional V-shape land portion block in which onlythe rigidity of the center portion is high, the block rigidity isincreased in the center portion having the bent portion, the portion ofthe V-shape land portion block 101 at the side of the tire equatorialline CL and the portion of the V-shape land portion block 101 at theouter side in the tire width direction. Consequently, the wear resistantperformance of the V-shape land portion block 101 is improved.

In the V-shape land portion block 101, the circumferential directionlength W1 of the inclined groove portion 161 located at one side (a sideof the tire equatorial line) in the tire width direction with respect tothe bent portion 163 is longer than the circumferential direction lengthW2 of the inclined groove portion 162 located at another side (a side ofthe tread end) in the tire width direction with respect to the bentportion 163.

Thus, in the V-shape land portion block 101, in order to prevent theland portion block from falling at the side of the tread end, namely inorder to increase the block rigidity, the circumferential directionlength of the land portion block at only one side in the tire widthdirection between the V-shape land portion blocks 101 adjacent to eachother in the circumferential direction is made long, and thecircumferential direction length of the inclined groove portion 162 ismade smaller than the circumferential direction length of the inclinedgroove portion 161. Accordingly, the most projected portion 110 a islocated at a position different from the most recessed portion 120 a.

(4.2) Center Land Portion Row 200

When the side wall in the circumferential direction of the inclined landportion block such as the land portion block 210 and the land portionblock 260 formed in the center land portion row 200, inclined againstthe tire width direction receives input in the tire circumferentialdirection, as shown in FIGS. 7A and 7B, the force in the vectordirection along the side wall at the tire circumferential direction enddoes not rotate the land portion block 210 (and the land portion block210P), while the input to the land portion block 210 along the vectordirection orthogonal to the side wall at the tire circumferentialdirection end generates moment to rotate the land portion block 210(counterclockwise rotation direction in FIGS. 7A and 7B).

The directions of the rotation moments generated in the crossinginclined groove 270 and the terminal inclined groove 220 are the same toeach other, and therefore the edge effects of the land portion blocksdue to the groove wall portions of the crossing inclined groove 270 andthe terminal inclined groove 220 are derived in the same direction.Thus, the block edge component is increased as the whole of the centerland portion row 200.

As shown in FIG. 7A, the rotation moments generated in the land portionblock 210 and the sipe 230 against the input in the tire circumferentialdirection to the land portion block 210 are generated in oppositedirections to each other, and thereby the rotation moments are cancelledto each other. Consequently, the deformation of the land portion block210 is suppressed.

Thus, compared to a configuration in which the sipe 230 (and the sipe290) and the crossing inclined groove 270 are extended in the samedirection, the block rigidity of the center land portion row 200 isincreased largely. In this way, since the block rigidity of the whole ofthe center land portion row 200 is increased, the ground contact area isincreased and the force pressing the land portion block 210 (and theland portion block 260) and the sipe 230 (and the sipe 290) against theroad surface is increased. With this, the edge effect is improved, sothat the on-ice performance can be improved and the wear resistantperformance can be improved.

Further, the terminal incline groove 220 and the notched groove 240 arelocated on the extension line of the crossing inclined groove 270.Further the hook-shaped groove portion 273 is formed at the end of thecrossing inclined groove 270. Thus, the block rigidity is secured andthe block edge component is increased by the grooves behaving like onelug groove crossing the center land portion row 200.

Further, the circumferential direction groove 60 is provided with thecircumferential direction groove portion 61 extended in the tirecircumferential direction and inclined against the tire circumferentialdirection, and the inclined lug groove portion 62 inclined in the samedirection as the terminal inclined groove 220 against the tire widthdirection. The block edge component is further increased by thecircumferential direction groove 60 extended in the tire circumferentialdirection in a non-linear manner.

In the center land portion row 200, the side walls 210 c, 210 d, 220 c,220 d located at the ends in the tire circumferential direction of theland portion block 210 and the land portion block 260 are inclinedagainst the tire width direction. Further, these side walls are inclinedin opposite direction to the sipe 230 and the sipe 290 against the tirewidth direction.

Accordingly, compared to a configuration in which the sipe 230 and thesipe 290 are extended in the same direction to these side walls, thedeterioration of the block rigidity of the center land portion row 200can be suppressed. With this, the on-ice performance can be ensured, andthe wear resistant performance can be improved.

As described above, the ratio S1/S2, which is the negative ratio of thecenter land portion row 200, indicates a ratio of the groove area in thecenter land portion row 200. In a case in which the negative ratio islarge, the area of the groove portion is large and therefore the edgeeffect by the block edge component is improved, while the area of theland portion block is small and therefore the block rigidity isdeteriorated. Consequently, the ground contact area is decreased and thewear resistant performance is deteriorated.

On the other hand, in a case in which the negative ratio is small, thearea of the groove portion is small and the area of the land portionblock is large, and therefore the block rigidity is increased, so thatthe ground contact area is increased and the wear resistant is improved,however the edge effect by the block edge component of the groove isdeteriorated.

Thus, the block rigidity of the center land portion row 200 is suitablyimproved by the terminal inclined groove 220, the terminal inclinedgroove 280 and the crossing inclined groove 270. In this way, byoptimizing the negative ratio of the whole of the center land portionrow 200, the block rigidity is increased and the ground contact area isincreased. Further, the force pressing the land portion block 210 andthe land portion block 260, and the sipe 230 and the sipe 290 againstthe road surface is increased. With this, the edge effect is improved,so that the on-ice performance can be improved and the wear resistantperformance can be improved.

Further, as described above, the ratio S1/S2 is preferably set in arange between 0.05 and 0.25. In a case in which the ratio S1/S2 is morethan 0.25, the negative ratio becomes large, and the area of the landportion block is largely decreased, and therefore the block rigidity isexcessively decreased. Consequently, the ground contact area is largelydecreased, and the wear resistant performance is largely deteriorated.

Further, in a case in which the ratio S1/S2 is less than 0.05, thenegative ratio becomes small, and the area of the groove portion islargely decreased, and therefore the draining performance is not securedat all. Further, the edge effect by the block edge of the groove islargely deteriorated.

(4.3) Shoulder Land Portion Row 300 in and Shoulder Land Portion Row300out

In the shoulder land portion row 300 in (the shoulder land portion row300 out is similar, hereinafter the same), the amplitude A1 of thecircumferential direction sipe 320 is larger than a size of theamplitude A2 of the width direction sipe 340 adjacent to thecircumferential direction sipe 320.

By setting the sipe interval to be large and by setting the pitch lengthof the land portion block 310 that forms the shoulder land portion row310 in to be small, the rigidity of the land portion block 310 isincreased and the ground contact area is increased. Further, the forcepressing the block edge and the sipe edge against the road surface isincreased and the edge effect due to and the increase of the block edgeis improved, and the wear resistant performance is improved.

However, if the block rigidity in the tire circumferential direction ofthe land portion block 310 is not deteriorated, it is preferable thatthe edge effect is large. Thus, by forming the circumferential directionsipe 320, which hardly decreases the rigidity in the tirecircumferential direction and derives the edge effect in the tire widthdirection, in the land portion block 310, the amplitude Al of the zigzagportion is made large. With this, the sipe edge in the tirecircumferential direction is derived, so that the edge effect in thetire circumferential direction can be improved.

Further, the circumferential direction linear sipe 351 having a linearshape and the circumferential direction linear sipe 352 having a linearshape are formed in the land portion block 310. The circumferentialdirection sipe 320, the circumferential direction linear sipe 351 andthe circumferential direction linear sipe 352 can increase the edgeeffect in the tire width direction.

In the shoulder land portion row 300 in, deformation of a portion of theland portion block 300 at a side of the tire equatorial line CL is notsuppressed contrary to a portion at a side of the tread end in which aninclined side wall of a buttress portion, which is a side wall at anouter side of the tread end, has high rigidity, and the ground contactlength of the portion at the side of the tire equatorial line CL islonger than that of the portion at the side of the tread end.

Thus, in order to derive the sipe edge largely, the end 332 of the widthdirection sipe 330 at the side of the tire equatorial line CL iscommunicated with the circumferential direction sipe 320. Further, theend 331 of the width direction sipe 330 is communicated with thecircumferential direction groove 40. Accordingly, the sipe edgecomponent of the land portion block 310 can be increased.

On the other hand, the end 341 of the width direction sipe 340 at theside of the tire equatorial line CL is not communicated with thecircumferential direction sipe 320 but terminated in the land portionblock 310. The side wall of the land portion block 310 at the outer sideof the tread end is different from the side wall at the side of the tireequatorial line CL and has high rigidity due to the inclined side wallof the buttress portion, and therefore the deformation of the side wallat the outer side of the tread end is suppressed. Further, the side wallat the outer side of the tread end has the ground contact length shorterthan that of the side wall at the side of the tire equatorial line CL,and thereby the block rigidity in the tire circumferential direction ofthe land portion block 310 is deteriorated by deriving the sipe edgelargely at the side of the tire equatorial line CL, while in order toincrease the block rigidity, the width direction sipe 340 at the outerside of the tread end is not communicated with the circumferentialdirection sipe 320 but terminated in the land portion block 310.Further, another end of the width direction sipe 340 is terminatedwithout being communicated with the main groove and the buttressportion.

Accordingly, although the block rigidity of the land portion block 310at the side of the tire equatorial line CL is deteriorated, since theblock rigidity at the outer side of the tread end is increased, theblock rigidity of the shoulder land portion row 300 in can be kept.Further, by keeping the block rigidity of the shoulder land portion row310 in, the ground contact area is secured and the edge effect by thesipe edge component is improved. Consequently, the on-ice performancecan be improved and the wear resistant performance can be kept.

Further, the end 341 of the width direction sipe 340 is located in therange of the amplitude A1. Further, the width direction sipe 340 islocated on the extension line of the width direction sipe 330communicated with the apex 323 of the circumferential direction sipe 320having a zigzag shape. With such a configuration, the edge effect by thesipe edge component can be further improved.

In the shoulder land portion row 300 in, the step portion 360 having anotched shape is formed in the side wall 310 b. The step portion 360 isformed at the end of the land portion block 310 at the side of the treadend in the tire width direction. The step portion 360 is provided withthe raised bottom surface 361. The raised bottom surface 361 is formedin a rectangular shape extended in the tire width direction.

Thus, by forming the step portion 360 formed to notch the land portionblock 310, the volume of the lug groove 70 formed between the landportion blocks 310 adjacent to each other is increased, and thereforeso-called snow column shearing force is increased. Further, the drainingperformance is also improved.

Further, the step portion 360 is formed at the end of the land portionblock 310 at the side of the tread end, and thereby ice and snow can beeasily taken in, and the ice and snow hardened as the snow column can bedrained easily.

Further, the step portion 360 is not formed as a deep groove bottomportion, and the step portion 360 is formed at the end at the side ofthe tread end. Specifically, the ice and snow hardened as the snowcolumn can be easily drained by the raised bottom surface 361.

Further, since the step portion 360 is formed, the side wall of the landportion block 310 at the circumferential direction end is bent at aposition of the step portion 360. Consequently, compared to the sidewall having a linear shape without the step portion 360, the block edgecomponent by the side wall 310 b of the land portion block 310 isincreased.

Further, since the raised bottom surface 361 is formed, the volume ofthe land portion block 310 at an upper side of the raised bottom surface361 (outer side in the tire width direction) is decreased, while theland block portion is formed by the step portion 360 at a lower side ofthe raised bottom surface 361 (inner side in the tire width direction),similar to the side of the tire equatorial line CL. Further, thedeformation of the land portion block 310 at the side of the tread endis suppressed by the inclined side wall of the buttress portion havinghigh rigidity, and thereby the block rigidity of the land portion block310 can be kept.

That is, with the step portion 360, the on-ice performance can beimproved and the wear resistant performance can be kept. Further, theon-snow performance and the draining performance can be improved.

(4.4) Relation Between Pitch and Sipe

As described above, it is preferable that a value of (the average sipeinterval h)/(the average pitch length L) is set to fulfill a relation of0.130≤(h/L)≤0.400. In a case in which the value of h/L is less than0.130, the pitch length is relatively large, while the sipe interval isextremely small. Accordingly, the number of the sipes is extremelylarge, and thereby the block rigidity of the land portion block becomesextremely low.

On the other hand, in a case in which the value of h/L is more than0.400, the sipe interval is relatively large, while the pitch length isextremely small. Accordingly, the number of the sipes is extremelysmall, for example one or two, however the pitch length is extremelysmall. Thus, even if the sipe interval is made large, the block rigidityof the land portion block is not increased to the contrary. Further, thesipe edge component is extremely decreased.

Further, as described above, it is preferable to fulfill the relation of140≤(h×L)≤350. In a case in which the value of (h×L) of the average sipeinterval and the average pitch length is less than 140 (mm)², the sipeinterval and the pitch length are excessively small. In a case in whichthe sipe interval is small, the land portion block is divided into smallportions, and therefore the block rigidity of the land portion block isdeteriorated. Further, in a case in which the pitch length is small, theblock rigidity of the land portion block is deteriorated. As a result,the block rigidity is excessively deteriorated.

On the other hand, in a case in which the value (h×L) is more than 350(mm)², the sipe interval and the pitch length are excessively large. Ina case in which the sipe interval is excessively large, although theblock rigidity of the land portion block is high, the number of thesipes is excessively small, and therefore the sipe edge effect is notderived. In a case in which the pitch length is large, although theblock rigidity is high, the number of the pitches in the wholecircumference of the tire is decreased, and therefore the block edgeeffect is extremely deteriorated. As a result, the edge effect isexcessively deteriorated.

Further, in a winter tire such as a studless tire, the ground contactlength becomes longer in the center region (center portion land portionblock), the second region (second portion land portion block), and theshoulder region (shoulder portion land portion block) in this order, andthe ground contact length of the center region is the longest. Thus, itis effective that the sipe edge and the block edge in the tirecircumferential direction in braking are derived by using long groundcontact length. By setting the sipe interval of the center region to besmaller than those in the second region and the shoulder region, theedge effect toward the circumferential direction is largely derived.

As described above, in the center portion land portion block, it ispreferable to fulfill the relation of 3.0 mm≤h≤7.1 mm. In a case inwhich h is less than 3.0 mm, the land portion block is divided intosmall portions and therefore the block rigidity is excessivelydecreased. On the other hand, in a case in which h is more than 7.1 mm,although the block rigidity is high, the number of the sipes isexcessively small, and therefore the sipe edge is not derived and thesipe edge effect is excessively deteriorated.

Further, it is necessary to enhance the block rigidity of the shoulderregion and the second region as the region becomes closer to a side ofthe tread end because the number of the sipes in the center portion ismade large. Further, the input of the lateral force is larger toward theside of the tread end, and the lateral force in the shoulder region isthe largest. Thus, in order to enhance the block rigidity, the sipeinterval is made large.

Further, as described above, in the shoulder land portion block, it ispreferable to fulfill the relation of 3.7 mm≤h≤8.5 mm. In a case inwhich h is less than 3.7 mm, the block is divided into small portions,and therefore the block rigidity is excessively deteriorated. On theother hand, in a case in which h is more than 8.5 mm, although the blockrigidity is high, the sipe edge effect is excessively deteriorated.Here, the numerical range of the average sipe interval in the secondregion is similar to that in the shoulder region.

Further, in the second region, the ground contact length is shorter thanthat in the center region and longer than that in the shoulder region.Thus, in order to enhance the sipe edge effect and to increase the blockrigidity, the sipe interval is set to be larger than that in the centerregion and smaller than that in the shoulder region. Further, based onthe same reason to the center region and the shoulder region, it ispreferable to set the average sipe interval in the second region withinthe range described above.

Further, as described above, the average sipe interval h of the landportion block of the whole of the pneumatic tire 10 is set in the rangebetween 3.4 mm and 7.9 mm. With this, the sipe interval is made largeand the number of the sipes is made small. Consequently, the blockrigidity is increased, and one sipe edge and one block edge of one landportion block are increased to a maximum range capable of increasing thesipe edge and the block edge.

In a case in which h is less than 3.4 mm, the land portion block isdivided into small portions, and therefore the block rigidity isexcessively deteriorated. On the other hand, in a case in which h ismore than 7.9 mm, although the block rigidity is high, the sipe edgeeffect is excessively deteriorated.

Further, as described above, it is preferable that the average pitchlength L of the land portion block of the whole of the pneumatic tire 10is set to fulfill the range of 19.2 mm≤L≤44.6 mm. In a case in which thepitch length is less than 19.2 mm, the pitch length is excessivelysmall, and therefore the block rigidity is excessively deteriorated. Ina case in which the pitch length is more than 44.6 mm, the pitch lengthis excessively large, and therefore the block rigidity is increased,however the number of the sipes in the whole circumference of the tireis decreased. Consequently, the block edge effect is largelydeteriorated to be excessively small.

More specifically, in a case in which the average sipe interval is lessthan 3.4 mm or the average pitch length is more than 44.6 mm, the sipeinterval is excessively small and the block is divided into smallportions, and thereby the block rigidity is excessively deteriorated.Further, in a case in which the pitch length is excessively large, thenumber of the pitches is decreased, and thereby the block edge effect isexcessively deteriorated. Further, even if the pitch length is madelarge, the block rigidity is not increased because the block is dividedinto the small portions by the sipes.

Further, in a case in which the average sipe interval is more than 7.9mm or the average pitch length is less than 19.2 mm, the sipe intervalis large, and therefore the block rigidity is increased, however thenumber of the sipes is excessively small, and thereby the sipe edge isnot derived and the sipe edge effect is excessively deteriorated.Further, the pitch length is small, and the block rigidity of each blockis excessively deteriorated. As a result, the total edge effect isdeteriorated, and the block rigidity is not increased.

Further, in a case in which the average sipe interval is less than 3.4mm or the average pitch length is less than 19.2 mm, although the sipeedge component is increased, the sipe interval is excessively small andthe block is divided into small portions, and thereby the block rigidityis excessively deteriorated. Further, since the pitch length is smalland the block rigidity of each block is excessively deteriorated, theblock edge effect is excessively deteriorated. Accordingly, the blockrigidity is excessively deteriorated, and the total edge is alsodecreased.

Further, in a case in which the average sipe interval is more than 7.9mm or the average pitch length is more than 44.6 mm, the sipe intervalis large, and therefore the block rigidity is increased, however thenumber of the sipes is excessively small, and thereby the sipe edge isnot derived and the sipe edge effect is excessively deteriorated.Further, in a case in which the pitch edge is excessively large, thenumber of the pitches is decreased, and thereby the block edge effect isexcessively deteriorated. Further, even if the pitch length is madelarge, the block rigidity is not increased because the block is dividedinto small portions by the sipe.

Further, in a standard tire size (hereinafter, referred to as standardtire size) having a tire width SEC (hereinafter the same) of 165, 175,185, 195, 205, 215, 225, 235, 245 or 255 in a tire for a passengervehicle (Passenger car tire), which is defined in the standard of JATAMA(or similar standard such as ETRTO, and TRA), it is preferable that theaverage sipe interval and the average pitch length are set to fulfillthe following ranges of

4.2 mm≤h≤6.3 mm

23.6 mm≤L≤35.4 mm.

Further, the tire width SEC denotes 195 (mm) in a tire of 195/65R15.

In the standard tire size, it is preferable that the average sipeinterval and the average pitch length of the center portion land portionblock are set to fulfill the following ranges of

3.7 mm≤h≤5.6 mm

23.6 mm≤L≤35.4 mm.

In the standard tire size, it is preferable that the average sipeinterval and the average pitch length of the shoulder portion landportion block are set to fulfill the following ranges of

4.5 mm≤h≤6.8 mm

23.6 mm≤L≤35.4 mm.

In the standard tire size, it is preferable that the average sipeinterval and the average pitch length of the second portion land portionblock are set to fulfill the following ranges of

4.1 mm≤h≤6.1 mm

23.6 mm≤L≤35.4 mm.

By fulfilling such relations, the sipe interval and the pitch length areoptimized. By appropriately decreasing the number of the sipes, theblock rigidity is increased, and by appropriately setting the pitchlength to be small, the number of the pitches and the number of theblocks are increased to enhance the block edge effect. Consequently, theblock rigidity can be increased and the total edge effect can beimproved. Further, the demerit of a configuration with the average sipeinterval and the average pitch length being out of the ranges describedabove are as described above.

Further, in a large tire size having the tire width SEC of 265, 275,285, 295 or 305 (hereinafter, referred to as large SEC tire size)defined in the standard of JATAMA, it is preferable that the averagesipe interval and the average pitch length are set to fulfill thefollowing ranges of

6.3 mm<h<7.9 mm

35.4 mm<L<44.6 mm.

In the large SEC tire size, it is preferable that the average sipeinterval and the average pitch length of the center portion land portionblock are set to fulfill the following ranges of

5.6 mm<h≤7.1 mm

35.4 mm<L≤44.6 mm.

In the large SEC tire size, it is preferable that the average sipeinterval and the average pitch length of the shoulder portion landportion block are set to fulfill the following ranges of

6.8 mm<h≤8.5 mm

35.4 mm<L≤44.6 mm.

In the large SEC tire size, it is preferable that the average sipeinterval and the average pitch length of the second portion land portionblock are set to fulfill the following ranges of

6.1 mm<h≤7.7 mm

35.4 mm<L≤44.6 mm.

With this, in the tire having such a tire size, the block rigidity canbe increased and the total edge effect can be improved.

Further, in a small tire size having the tire width SEC of 135, 145 or155 (hereinafter, referred to as small SEC tire size) defined in thestandard of JATAMA, it is preferable that the average sipe interval andthe average pitch length are set to fulfill the following ranges of

3.4 mm≤h<4.2 mm

19.2 mm≤L<23.6 mm.

In the small SEC tire size, it is preferable that the average sipeinterval and the average pitch length of the center portion land portionblock are set to fulfill the following ranges of

3.0 mm≤h<3.7 mm

19.2 mm≤L<23.6 mm.

In the small SEC tire size, it is preferable that the average sipeinterval and the average pitch length of the shoulder portion landportion block are set to fulfill the following ranges of

3.7 mm≤h<4.5 mm

19.2 mm≤L<23.6 mm.

In the small SEC tire size, it is preferable that the average sipeinterval and the average pitch length of the second portion land portionblock are set to fulfill the following ranges of

3.3 mm≤h<4.1 mm

19.2 mm≤L<23.6 mm.

With this, in the tire having such a tire size, the block rigidity canbe increased and the total edge effect can be improved.

As described above, the value of (the average block edge componentDball/the average sipe edge component Dsall)/average block rigidity G ispreferably set to fulfill the relation of 2.20≤(Dball/Dsall)/G≤4.00. Ina case in which the value of (Dball/Dsall)/G is less than 2.20 (mm)³/N,although the sipe edge component is extremely large against the averageblock rigidity of the land portion blocks, the block edge component isextremely decreased. This is because the number of the sipes is largeand the sipe interval is small, and thereby the block rigidity isexcessively deteriorated.

On the other hand, in a case in which the value of (Dball/Dsall)/G ismore than 4.00 (mm)³/N, although the block edge component is extremelylarge against the average block rigidity of the land portion blocks, thesipe edge component is extremely decreased. This is because the numberof the sipes is small and the sipe interval is large, and thereby theblock rigidity is excessively increased.

Further, the width direction sipe may be inclined against the tirecircumferential direction (tire equatorial line CL) as long as the widthdirection sipe is extended in the tire width direction because the edgecomponent of the tire circumferential direction is generated.

As described above, the value of (the average block edge componentDball)/(the average sipe edge component Dsall) is preferably set tofulfill the relation of 0.15≤(Dball/Dsall)≤0.48. In a case in which thevalue of Dball/Dsall is less than 0.15, although the sipe edge componentis made extremely large, the block edge component is extremelydecreased. This is because the number of the sipes is large and the sipeinterval is small, and thereby the block rigidity of the land portionblock is excessively deteriorated.

On the other hand, the value of Dball/Dsall is more than 0.48, althoughthe block edge component is made extremely large, the sipe edgecomponent is extremely decreased. This is because the number of thesipes is small and the sipe interval is large, and thereby the blockrigidity of the land portion block is excessively increased.

As described above, the value of (the average sipe interval hs of theshoulder portion land portion block)/(the average sipe interval hc ofthe center portion land portion block) is preferably set to fulfill therelation of 1.05≤(hs/hc)≤4.00. In a case in which the value of hs/hc isless than 1.05, the sipe interval of the shoulder portion land portionblock is small, and thereby the number of the sipes is made large andthe block rigidity of the land portion block is extremely deteriorated.Further, although the sipe edge component is increased, the block edgecomponent is excessively decreased.

On the other hand, in a case in which the value of hs/hc is more than4.00, the sipe interval of the shoulder portion land portion block islarge, and thereby the number of the sipes is made excessively small.Consequently, although the block edge component is increased, the sipeedge component is excessively decreased.

Further, other numerical ranges relating to the pitch and the sipedescribed above are determined so as to derive both of the blockrigidity of the land portion block and the edge component as describedabove. With this, the on-ice performance and the wear resistantperformance can be obtained at a high level.

(4.5) Evaluation Test

Next, a method and a result of an evaluation test performed to check therelation between the average sipe interval and the average pitch lengthwill be further described.

Table 1 shows a specification and a test result (on-ice brakingperformance and wear resistant performance) of each of pneumatic tires(studless tires) according to examples. Table 2 shows a specificationand a test result of each of (studless tires) according to aconventional example, comparative examples and the examples.

Further, Table 3 through Table 6 show results of an additional test ofeach of the pneumatic tires (studless tires) according to thecomparative examples and the examples.

TABLE 1 No 2 3 4 5 6 7 8 NOTE EXAMPLE 1 EXAMPLE 2 EXAMPLE 3 EXAMPLE 4EXAMPLE 5 EXAMPLE 6 EXAMPLE 7 SIPE INTERVAL/ h/L 0.18 0.13 0.18 0.180.18 0.18 0.18 PITCH LENGTH SIPE INTERVAL * h * L 65.2 35.6 99.2 153 6223 3 308.1 352.3 PITCH LENGTH AVERAGE SIPE h 3 40 3 90 4.20 5 20 6.30 740 7 90 INTERVAL(mm) CENTER PORTION he 3.0 3.5 3 7 4 7 5.6 6.6 7.1 SIPEINTERVAL(mm) SECOND PORTION h2 3.3 3 8 4.1 5.1 6.1 7.2 7.7 SIPEINTERVAL(mm) SHOULDER PORTION hs 3.7 4 2 4.5 5.7 6.8 8 0 8.5 SIPEINTERVAL(mm) AVERAGE PITCH L 192 22.0 23.6 295 354 416 44.6 LENGTH(mm)ON-ICE BRAKING 104 109 112 115 108 104 101 PERFORMANCE WEAR RESISTANT107 112 119 125 127 130 134 PERFORMANCE

TABLE 2 No. 1 2 3 4 5 6 COMPAR- COMPAR- COMPAR- COMPAR- COMPAR- CON-ATIVE ATIVE ATIVE ATIVE ATIVE VENTIONAL NOTE EXAMPLE 1 EXAMPLE 2 EXAMPLE3 EXAMPLE 4 EXAMPLE 5 EXAMPLE SHOULDER PORTION hs/hc 0.82 0.82 0.82 0.890.92 1.00 SIPE INTERVAL/ CENTER PORTION SIPE INTERVAL SECOND PORTIONh2/hc 0.82 0.89 1.00 0.82 1.12 1 00 SIPE INTERVAL/ CENTER PORTION SIPEINTERVAL SHOULDER PORTON hs/h2 1.00 0.92 0.82 1.09 0.82 1.00 SIPEINTERVAL/ SECOND PORTION SIPE NTERVAL ON-CE BRAKING 97 97 97 98 99 100PERFORMANCE WEAR RESISTANT 122 125 130 127 118 100 PERFORMANCE No. 7 8 910 11 EXAMPLE 1 EXAMPLE 2 EXAMPLE 3 EXAMPLE 4 EXAMPLE 5 SHOULDER PORTION1.00 1.12 1.21 1.21 1.21 SIPE INTERVAL/ CENTER PORTION SIPE INTERVALSECOND PORTION 1.21 092 1.00 1.09 1.21 SIPE INTERVAL/ CENTER PORTIONSIPE INTERVAL SHOULDER PORTON 0.89 1.21 1.21 1.12 1.00 SIPE INTERVAL/SECOND PORTION SIPE NTERVAL ON-CE BRAKING 105 110 112 115 108PERFORMANCE WEAR RESISTANT 107 120 104 111 113 PERFORMANCE

TABLE 3 ADDITIONAL EXAMPLE - COMPARATIVE EXAMPLE NOTE 1 2 3 4 5 6 SIPEINTERVAL/PITCH LENGTH h/L 0.12 0.13 0.14 0.20 0.25 0.45 SIPE INTERVAL *PITCH LENGTH h * L 168.8 188.0 178.6 128.2 100.0 142.2 AVERAGE SIPEINTERVAL(mm) h 4.5 5.0 5.0 5.0 5.0 8.0 CENTER PORTION SIPE INTERVAL(mm)he 5.0 4.5 4.5 4.5 4.5 7.1 SECOND PORTION SIPE INTERVAL(mm) h2 4.5 4.94.9 4.9 4.9 7.8 SHOULDER PORTION SIPE INTERVAL(mm) hs 4.0 5.5 5.5 5.55.5 8.6 AVERAGE PITCH LENGTH(mm) L 37.5 37.6 35.7 25.6 20.0 17.8 ON-ICEBRAKING PERFORMANCE 97 106 107 108 109 95 WEAR RESISTANT PERFORMANCE 96113 112 120 118 130

TABLE 4 ADDITIONAL EXAMPLE - ADDITIONAL COMPARATIVE EXAMPLE NOTE 1 2 3 45 6 7 AVERAGE BLOCK/ P 0.30 0.45 0.47 0.35 0.40 0.50 1.00 SIPE EDGECOMPONENT SECOND PORTION/ P2/Pc 1.50 2.60 4.10 1.13 1.10 1.10 5.90CENTER PORTION (SHOULDER PORTION/ (Ps/P2) * 1.50 0.50 0.30 2.90 3.503.80 0.10 SECOND PORTION) * (Pc/P2) (CENTER PORTION/ SECOND PORTION)CENTER PORTION BLOCK/ Pc 0.15 0.19 0.14 0.18 0.19 0.22 0.29 SIPE EDGECOMPONENT SECOND PORTION BLOCK/ P2 0.23 0.50 0.57 0.20 0.21 0.25 1.71SIPE EDGE COMPONENT SHOULDER PORTION BLOCK/ Ps 0.52 0.65 0.70 0.67 0.801.03 1.01 SIPE EDGE COMPONENT ON-ICE BRAKING 109 98 102 106 104 102 106PERFORMANCE WEAR RESISTANT 122 110 106 111 113 92 85 PERFORMANCE

TABLE 5 ADDITIONAL EXAMPLE - COMPARATIVE EXAMPLE NOTE 1 2 3 4 5 6 7 8(AVERAGE BLOCK/ R 2.00 2.28 2.50 3.13 3.50 3.60 3.30 4.10 SIPE EDGECOMPONENT)/ AVERAGE BLOCK RIGIDITY SECOND PORTION/ R2/Rc 1.00 1.11 1.201.47 1.85 0.78 1.10 1.00 CENTER PORTION SHOULDER PORTION/ Rs/R2 1.001.04 1.20 1.50 1.85 3.00 2.60 1.00 SECOND PORTION CENTER PORTION Rc 2.002.10 2.06 2.01 1.67 2.62 2.00 4.10 SECOND PORTION R2 2.00 2.33 2.47 2.953.10 2.04 2.20 4.10 SHOULDER PORTION Rs 2.00 2.42 2.97 4.43 5.73 6.135.71 4.10 ON-ICE BRAKING 100 102 107 115 108 104 106 70 PERFORMANCE WEARRESISTANT 100 104 111 125 108 106 108 140 PERFORMANCE

TABLE 6 ADDITIONAL EXAMPLE - COMPARATIVE EXAMPLE NOTE 1 2 3 4 SHOULDERPORTION hs/hc 2.20 1.60 4.02 9.00 SIPE INTERVAL/ CENTER PORTION SIPEINTERVAL SECOND PORTION h2/hc 1.07 1.08 7.03 4.10 SIPE INTERVAL/ CENTERPORTION SIPE INTERVAL SHOULDER PORTION hs/h2 2.06 1.48 0.57 2.20 SIPEINTERVAL/ SECOND PORTION SIPE INTERVAL ON-ICE BRAKING 104 106 94 93PERFORMANCE WEAR RESISTANT 114 116 108 NA PERFORMANCE

(4.5.1) Basic Configurations of Tires for Evaluation Test and TestCondition

A size of each of pneumatic tires used for the evaluation test and atest condition are as described below.

Tire size: 195/65R15

Rim size: 6J×15

Air pressure: 240 kPa (front tire and rear tire)

Vehicle: Anti-lock brake system (ABS) installed vehicle

Further, the tread pattern having a shape shown in FIG. 3 is adopted.“The on-ice braking performance” corresponds to an average value of fivevalues excluding the maximum value and the minimum value after adistance (braking distance) to stop the vehicle by performing hardbraking at a speed of 20 km/h (ABS activated) on an ice road test courseat each of a stage of a new tire and a stage after initial travelling ismeasured at seven times. Further, the on-ice braking performance isindexed against the tire according to the conventional example(comparative example 1) defined as 100. As the value is larger, thebraking distance is shorter and the on-ice braking performance ishigher.

“The wear resistant performance” is evaluated based on a remaininggroove depth after a test target tire is mounted to the vehicle on whicha weight corresponding to two passengers is mounted and the vehicle istravelled on an asphalt pavement road for 10,000 km. Specifically, thewear resistant performance is indexed against the remaining groove depthof the tire according to the conventional example (comparativeexample 1) defined as 100. As the value is larger, the remaining depthis deeper and the wear resistant performance is higher.

(4.5.2) Evaluation Test Result

As shown in Table 1, in the tires according to the examples (No. 2through No. 8), “the on-ice braking performance” and “the wear resistantperformance” are improved. In particular, in No. 4 through No. 6, bothof the performance are balanced well and improved largely.

Further, as shown in Table 2, by setting the value of (hs/hc) of thesipe intervals of the shoulder portion land portion block (shoulderportion) and the center portion land portion block in the rangedescribed above, in the tire according to the examples 1 through 5, “theon-ice braking performance” and “the wear resistant performance” areimproved compared to the tire according to the conventional example.

As shown by the test results in Table 1 and Table 2, in a case in whichthe priority is given to “the wear resistant performance”, it isimportant that the average pitch length and the average sipe intervalare set to be large. On the other hand, in a case in which the priorityis given to “the on-ice braking performance” while improving the wearresistant performance, it is not always important that the average pitchlength and the average sipe interval are merely set to be large, whileit is important that the average pitch length and the average sipeinterval are set to be balanced well.

This is because, as described above, almost all of the vehicles inrecent years normally have ABS and therefore the braking is repeated ina range having a relatively small slip ratio in which the ABS isactivated (namely, a range having high friction coefficient (μ)) ratherthan in a range having a large slip ratio in which the tire is lockedcompletely and slipped on the ice road surface. In such a case, theon-ice braking performance is improved by securing some extent of theblock rigidity of the land portion block rather than by forming manysipes.

Table 3 shows, similar to Table 1, a test result relating to the averagesipe interval and the average pitch length. Table 4 shows a test resultrelating to the sipe edge component. Table 5 shows a test resultrelating to the average block rigidity. Table 6 shows, similar to Table2, a test result relating the sipe interval.

As shown in Table 3 through Table 6, in the additional examples, “theon-ice braking performance” and “the wear resistant performance” areimproved.

(5) Other Embodiment

As described above, the contents of the present invention are describedwith reference to the examples, however the present invention is notlimited to those descriptions. It is obvious for a person skilled in theart to adopt various modifications and improvement.

For example, in the embodiment described above, the center land portionrow 200 is arranged at the position including the tire equatorial lineCL, and the V-shape land portion row 100 is arranged at the outer sidein the tire width direction of the center land portion row 200. However,the center land portion row 200 is not necessarily arranged at such aposition. Further, the V-shape land portion row 100 may be arranged atthe position including the tire equatorial line CL.

Further, the position of each of the shoulder land portion row 300 inand the shoulder land portion row 300 out is not limited in the shoulderregion and therefore the shoulder land portion row 300 in and theshoulder land portion row 300 out may be arranged in the second regionor the like.

Further, in the embodiment described above, both of the sipes 130, 140and the terminal inclined groove 150 are formed in the V-shape landportion block 101. However, only one of the sipes 130, 140 and theterminal inclined groove 150 may be formed in the V-shape land portionblock 101.

Further, in the embodiment described above, the circumferentialdirection length of the V-shape land portion block 101 is set to belonger than the width direction length of the V-shape land portion block101. However, the circumferential direction length may be the same asthe width direction length.

As described above, the embodiments of the present invention aredescribed, however the present invention is not limited to thedescription and the drawings forming a part of the present disclosure.Various modifications, examples, and operation techniques will beapparent from the present disclosure to a person skilled in the art.

The entire contents of Japanese Patent Application No. 2015-221897(filed on Nov. 12, 2015) are incorporated herein by reference.

INDUSTRIAL APPLICABILITY

According to the tire described above, the tire being capable oftravelling on ice and snow roads including an ice road surface andcapable of deriving performance on the ice road surface, performance ona dry road surface, and especially wear resistant performance at a highlevel.

REFERENCE SIGNS LIST

-   10, 10A pneumatic tire-   20 tread-   30, 40, 50, 60 circumferential direction groove-   61 circumferential direction groove portion-   62 inclined lug groove portion-   70 lug groove-   70 b groove bottom-   80 lug groove-   100 V-shape land portion row-   100 a, 100 b, 100 c, 100 d, 100 f, 100 g side wall-   101, 101A, 101B V-shape land portion block-   110 projection portion-   110 a most projected portion-   111, 112 projection portion side wall-   120 recess portion-   120 a most recessed portion-   121, 122 recess portion side wall-   130 sipe-   131 end-   140 sipe-   141 communication sipe-   141 a end-   142 communication sipe-   150 terminal inclined groove-   151 end-   160 width direction inclined groove-   161 inclined groove portion-   162 inclined groove portion-   163 bent portion-   170 notched recess portion-   200 center land portion row-   201, 202 land portion row-   210, 210P land portion block-   210 a, 210 b 210 c side wall-   220 terminal inclined groove-   220 c side wall-   221 end-   230 sipe-   231 communication sipe-   240 notched groove-   241 distal end-   260 land portion block-   270 crossing inclined groove-   271 first groove width portion-   272 second groove width portion-   273 hook-shaped groove portion-   280 terminal inclined groove-   281 end-   290 sipe-   300 in, 300 out shoulder land portion row-   310 land portion block-   310 a side wall-   310 b side wall-   320 circumferential direction sipe-   321 linear portion-   322 linear portion-   323 apex-   330 width direction sipe-   331, 332 end-   340 width direction sipe-   341 end-   351, 352 circumferential direction linear sipe-   352 a, 352 b end-   360 step portion-   361 raised bottom surface-   362 end-   380 zigzag surface-   A1, A2 amplitude-   CL tire equatorial line-   CT center position-   W1, W2 circumferential direction length

1. A tire comprising: a circumferential direction groove extended in atire circumferential direction; a lug groove extended in a tire widthdirection; and a plurality of blocks defined by the circumferentialdirection groove and the lug groove, wherein: at least one of the blocksincludes one or more sipes extended in the tire width direction; and asan average sipe interval hc is defined by an average interval of thesipes adjacent to each other in the tire circumferential direction in acenter portion block, which is the block arranged at a positionincluding a tire equatorial line, and an average sipe interval hs isdefined by an average interval of the sipes adjacent to each other inthe tire circumferential direction in a shoulder land portion block,which is the block located at a ground contact end in the tire widthdirection, a relation of 1.05≤(hs/hc)≤4.00 is fulfilled.
 2. The tireaccording to claim 1, wherein, as an average sipe interval h₂ is definedby an average interval of the sipes adjacent to each other in the tirecircumferential direction in a second land portion block, which is theblock located at an outer side in the tire width direction of the centerportion block, a relation of 1.00≤(h₂/hc)≤7.00 is fulfilled.
 3. The tireaccording to claim 1, wherein, as an average sipe interval h₂ is definedby an average interval of the sipes adjacent to each other in the tirecircumferential direction in a second land portion block, which is theblock located at an outer side in the tire width direction of the centerportion block, and the average sipe interval hs is defined by theaverage interval of the sipes adjacent to each other in the tirecircumferential direction in the shoulder land portion block, which isthe block located at the ground contact end in the tire width direction,a relation of 0.97≤(hs/h₂)≤2.15 is fulfilled.